I stuffed mine up pretty badly back in March (bruising came through from the torn muscle, had to hop on stairs, could barely climb since I couldnt pull on anything with my left leg etc.)
I thought it was going to be a horribly long term, non full recovery thing.
But it is pretty much completely better now
I went to a physio as soon as I did it and she gave me a bunch of stretches for that area.
1. Lie on back and slowly pull leg towards you with bent knee, stop when it hurts and hold for a while
after a few reps of this
2. Do the same, but before you reach the point where you got some pain, let the leg fall out to the side (like a one legged frog look)
3. Place leg on a chair and stretch the hamstring out that way, change the direction you face to work the groin a bit more.
4. Place leg on chair with partially bent leg and stretch that as well (works a different part of the hammy)
5. I also did some massage with tiger balm most days which really seemed to help, try to avoid getting it too high up the leg though, unless you are into that sort of thing...
In terms of actually improving those muscle groups...I dont have a clue, I seem to ruin one of them every so often when I dont use my heels properly, I guess I should just try more and try harder to use them properly instead of just sitting back on them.