Oh, wow, I'm shocked - SHOCKED! - that people on this forum don't have a Ph.D. in warm-up routines. I mean, it's not like they've been riding for years without incident or anything. You're right, of course, but geez, calm down.
So, you want to know the secrets of the "serious cyclists" on this forum? Well, let me tell you, it's not like we're hiding it from you. Dynamic stretching, mobilization, and exercises that target specific muscle groups? Yeah, no kidding. But, hey, I suppose it's nice of you to remind everyone.
For the record, I do some leg swings, hip circles, and calf raises. And, oh, the horror! I also do some light cardio to get my heart rate up. But, I'm sure that's not good enough for you. So, go ahead, enlighten us with your superior knowledge of warm-up routines. We're all ears... or, at least, one ear, because the other one is tired of listening to lectures.