-the identity of the seer or native, who wishes to alleviate something
-the thing wishing to be improved or changed 
-the motivation for such a desire 
-the nature or the identity of the cause of the negative
-the negative itself, and it's necessity in their life already (or it's place in their lesson set) 
-the practice, technique or structure of the remedial measure and even more things...

So there are many factors to examine and question here.

In some cases of consciousness, the mere thought of "remedial measure" becomes difficult to believe, such as in the case of the absolutist vision of the necessity and perfection of karma itself, which is arguably the highest vision to hold, in which case, no such measure are desired or 
believed in at all.

Perhaps better than that is when the seer believes that the penultimate remedial measure is either complete disassociation with the cause of the connection of the seer to the karma, as in the case of those philosophically tracking with Adi Sankaracarya.

Similar to that is how it is with those tracking with Vaishnava thought Acaryas, who recommend seeing all such negative karmas as perfect mercy for our detachment from matter, and who thus use only attachment to Vishnu Bhakti as the one and only necessary remedial measure, and thus, use elements of such Bhakti as their only measure, doing more sadhana, doing more praying, etc., in all negative cases in life. This is why advanced Vaishnavas for example hardly care about their charts or dashas etc., except in a whimsical passing fashion like a pastime for fun or passing interest.

Then there are those who are seeing on the platform of Karma Khanda, or Mimansha, and other karmic operating philosophical views, and these persons (which include most Westerners) have so many options to look into. This is where we usually discuss on this list- from the level of "it's my karma, and I can change it myself through thought, action, puja, yoga, etc.".

Many of the advanced Jyotishis on this list and elsewhere are halfway or more involved in one of the two first mentioned philosophical paths, knowingly or unknowingly, and thus we sometimes see that responses from them are mixed between karmic corrective methods, and the methods coming from their higher philosophical views, which are growing in them.

At the time of death, there isn't much time left to arrange for yagyas. So, many materially based measures are dependent upon a certain set of material conditions in order to be started or carried out. Thus, they are by definition of the material plane more so than say prayer.

The ultimate measure is an attitude adjustment. Indeed, a Saint is a person who primarily has a different attitude and belief about life than a regular person. It's not so much what they do, puja, yagya, etc., so much as how they think and feel spontaneously, all the time. Saints have
no problem with negativity's. This is one of their hallmarks. They are "surrendered" to Divine Will. Whereas, the normal person, is not, and try's to fix perceived negativity's in various ways.

So the ultimate remedial measure is the one that removes us from interest in the negativity's at all. 

For the attached person, remedial measures are the most interesting. 

Generally, a remedial measure consists of appeasing a Planetary God who is currently poised in this life to do negative harm to the positive material life of the native. So, some authorized puja or yagya is performed in honorific fashion of the God involved, and the native is the beneficiary. It's basically like filling out a "mercy request application" and submitting it. That's what a yagya essentially is. The priests are helping you to "fill in the form" in the proper way. In this sense, the puja or yagya is the "proper form" to fill out, "the one that will be heard" in the heavens.

However, karma is very balanced to begin with. So, if you try to change one side, it won't work unless you change the other. For example, you cannot kill your neighbors and expect them to like you. So, if you want their forgiveness for past aggressions, it's best to stop aggressing. So with our karma, if we wish to remove the 

RE-ACTION

we have to also remove the original cause or

ACTION

that causes the reaction. 

This is generally the case.

If one just removes the ACTION, then the RE-action will also dissipate
in due order.

So therefore the most thoughtful of all persons will recommend always soul searching for your inner connection to the action itself, and then removing that with means of inner work, one then removes the re-action as well. This is going on in all of us always. When we try to exercise for example, we are hoping for a certain result, but really what we're doing is trying to remove the action or element in us of laziness, and as laziness goes on every cell level in us, then our body visibly transforms externally, and we achieve the result our attachment wants.  But what really happened was through tapasya and austerity (the exercise) we changed our inner nature on the bodily level, and thus we got the fruit of a transformed body.

On a very subtle level, if one feels that a planet overall is harming them repeatedly throughout life, they may wish to apply for a "break" from that God, through Yagya. Japa is also a yagya, as are many other practices one can do for free, for oneself. 

Yesterday I received an email from Richard Brown, head of a Gemological Study group here on Earth, who is also a Gem Dealer. Richard is always pushing the science of Jyotish forward, especially in relation to Gems and these types of matters in general. So he has published on his
website a listing of the 108 names of each planet. One can chant the names of the planet(s) they wish to appease. I personally think this is a very HIGH way of remedial measure, with maximum potent effect. 

Sound is very powerful and subtle. Chanting the names of a planet with whom you are currently misalligned is certainly the quickest way to realign oneself properly with that division of Gods energies.

I noticed for example that one of Ketu's names is "Bhakta Rakshaka". This stood out to me as it was the name of my Gurudev as well, or his was Bhakti Rakshaka, or the protector of Bhakti. Bhakta Rakshaka means the "Guardian of the devoted". So, Ketu protects the devoted. If someone is misaligned with Ketu, they therefore may not be very well aligned with protection of the devoted persons. They may not therefore properly understand devotion. Chanting this mantra will help them to accept devotion and devotees as something needing protection. This will help their heart for example.

I highly believe mantra is the most powerful of practices. It is practical, and can be started even with a hardened heart. It is not something you have to be qualified to do, you just have to do it. It's
free, Vedic without question, harmless without question, and if done sincerely, possibly the most fruitful of all attempts.

Krishna also says that if we devote ourselves to getting fruits from the Gods, like removal of bad karma, we will quickly get results. He implies this is done as a part of nature to increase one's faith and involvement in the process of reciprocating with Gods in general but that the ultimate problem and need of the soul is a little higher than that preoccupation. After all, generally speaking, we are, with "remedials" aiming to fix something in one life, and not trying to fix the whole process of our involvement with matter, which is spoken of in Gita and Bhagavatam as something higher than pursuing "fixing this one life". 

I personally am not able to sort out all these things so well personally. It's a huge mess, this science of life. Wow. However, the basic inner attitude of service, surrender, and detachment from specific
desires is I find always helpful in tolerating life in a more positive way. 

For a person on an expansive karmic path, that is, one who is seeking still fulfillment of desires in this world, there is not choice but to make deals with Gods, through remedials, and try to move on towards one's goal. The retractive or exiting path is different, in which case one seeks to improve their tolerance of what is, rather than trying to change it. This is why we hear of lepers who "put the worms back into their wounds when they fall out onto the ground". When we hear of such things, we know we are dealing with a person who is of the mind that they are leaving this plane. They have little interest left in maintaining body and soul together for some material aim.

Hinduism can be very confusing in this way, as there are teachers and preachers on many different levels of realization. 

Therefore, before proceeding with such a discussion, it is good to nail down a few things, namely, what do you believe, and what is your honest hope and aim. These will at least establish which field, plane, or level you are operating on truly, and thus you can make real progress forward from that point honestly, and will more likely find your way to the practices which really work for where you're really at.

Like if one is out and out materialistically aiming, and really doesn't have interest or time for liberation, surrender, devotion, etc., then yagyas and pujas you pay others to do on your behalf may be the best option, along with Gems, etc. These are things that don't necessarily require a change of heart, but which may align you in a subtly mechanistic way with higher forces. Yogic practices were supposedly used by "Rakshashas" in scriptures to achieve their aims, though they were opposed to Vishnu's dominion in general. So the Vedas seem to imply that even evil person can use yoga, yagya, yantra, tantra, etc., in order to improve their experience in the material energy. I believe this is so, knowing God to be such an unbiased provider of whatever we desire.

So by applying in a sincere way, usually results can be had. Even those who are essentially materialistic will be "heard" if they perform such applications for alleviation of negatives. This is Krishna's implied promise. So go for it, by whatever means makes the most sense to you.

Know that Yagya is essentially formed by proper mantra chanting. So again, mantra chanting is such a potent force. Then with that use the directions, the days of the week, the hours of the day, and so on, all related to the planet(s) in question. Articles and artifacts, mantras, directions, times, and so on, are what make up yagya. 

If you were going to "get a loan" from a bank, you would "dress up" before going to the bank, in order to "show them you're worthy" of the loan, and able to "handle repayment".  Yagya is like that- you dress up, you gather the articles of your application, things that prove you are ready for the change or loan, and then you make your application, and hope for the right result. If it is not granted, you try again later after re-gathering the same things, but maybe hopefully in a little
better way this time around. So you try, try, try again, to get what you want.

Or you back off and try to go with the flow of your karma without changing it. Yoga is more so this approach in general. Yoga is more a process of working with, rather than changing. 

Since most of us are mixed between karmic and devotional paths and methods indeed, so therefore some of each may seem to be the right mix to propel us forward nicely, i.e., a gem may help with things which help with devotion, which helps with the other, and thus they yin yang together in an upward spiral. Eventually, some practices are left off in one's life as it improves, and others are taken up. Progressive and positive spiritual movement forward will be the result of the right mix. Our mood should improve. That is the ultimate aim. The ultimate aim is "happiness at all times" or at least a peacefulness filling the consciousness, despite all circumstances.

I hope I am somewhat correct in this forward attempt at explaining this subject according to my learning thus far. I am humble that I may need correction on many levels.