If I feel exhausted, I might do a headstand (sirsasana) or legs against the wall pose (vipariti karani).
If my low back hurts, I might do a kneeling groin stretch, a sit up, locust upper body keeping my legs on the ground, or stomach turning pose.
One of the benefits of learning yoga is that it gives you your very own toolbox so that you can make yourself feel better in literally any situation.
There are generally accepted sequences that many yoga masters have developed.
You could follow astanga first series on a regular basis, or follow the order recommended by Mr. Iyengar.
In Iyengar yoga, it’s generally recommended to do hip work and standing poses on Mondays, with some form of inversions and savasana.
On Tuesday, standing and seated twisting poses are recommended, hamstring stretches counterbalanced with forward folds and shoulderstand.
On Wednesday, Iyengar yoga prescribes sun salutes, shoulder series, triangles, twisting triangles and backbends.
On Thursday, standing poses are recommended along with balance poses.
On Friday, seated and supine poses are on the menu.
On Saturday and Sunday, the focus is on headstand and shoulderstand. Warm up with sun salutes or the five basic standing poses.
This could be a good way of going about organizing your practice, or you can learn to recognize the four or five or six poses that do the best job of shifting your energy.
You will know what these are because you will really enjoy doing them and it will be easy to talk yourself into practicing them.
Although it is a generally good idea to develop a well-rounded yoga practice so that you balance your muscles, I tend to recommend that people begin with the poses that make them feel the best.