I stretch AFTER every training ride. I'll stretch after a warm-up before a race, but not always. Before a race I tend to focus on the inside of my quads, and the groin. That area bothers me when I get low and fast sometimes.
My routine after a ride is always the same. I don't hold anything very long, probably 30-45 seconds each.
Using a wall I lean against it and stretch my toes, then achilles, then calf, then hamstring, then groin, then do the other leg.
Then while standing I spread my legs wide and go down to each foot, and then the center, and then stretch backwards from the center working the groin again.
I then do one standing hamstring (touch toes thing), and then one left over right, then right over left, then another hamstring.
I then work the back of my quads by standing, putting one foot out in front, and getting my chest down to my knee of that leg. I do both legs, then do a standing quad stretch.
After both quads I sit down and do my groin with a butterfly stretch (I'm not a huge fan of this as it hurts my knees sometimes). While sitting I put one leg straight out, bend other leg over it, and stretch my back by twisting. From that position I pull the leg that's crossed over towards my chest, which stretches the glutes. I repeat that on the other leg, then I'm done.
If I do my core workout I'll also stretch my core by doing the reach for the stars thing.
If anyone has a good upper back stretch, or neck/top shoulder area, I'd love to hear them. I have some neck and upper back trouble that I haven't solved yet.