I'm about as flexible as a Popsicle stick.
A few things that have helped over the years:
- Spend some significant part of your warmup in the drops (at home or on the track). This is "active stretching".
- On the road, do all efforts in the drops not the hoods. Also active stretching.
- After road rides, after I load up my bike, I'll step on the rear bumper and do deep glute and hamstring stretches. 2x15s on each leg.
- After track rides, I'll step on a bench and do deep glute and hamstring stretches. 2x15s on each leg.
- After a gym session, spend some time stretching. 2x15s for each leg = around 60s including transition time.
- I'll do "pigeon" stretches in bed if I'm especially tight and can't sleep. These are AWESOME.
I prefer head down:
For all stretches,
- Focus on feeling the muscles release tension.
- Stretching when cold or tight can lead to a muscle pull. Be cautious.
- Early in the winter when I'm lifting more or early in the spring when I'm riding more and I'm super tight, I'll sit in a hot bath to warm up the leg and back muscles then ask my wife to help me with partner stretches.
I haven't done much of this lately because I'm lazy. But, when I was most flexible, that's generally the menu I'd choose from.