After you have warmed the spine up in the beginning of a Vinyasa or even some Hatha classes, what is next are the "sun salutations". These are meant to further warm up the spine and the entire body in a forward and backwards motion.
Typically no side work or hip opening happens in what we call the sun salutations. Having said that, you may vary them all you desire, and I often do after one or two rounds of sun A's. Adding a few deep lunges, some twists and a warrior or two here and there.
Here's a link on how to do the traditional sun A. Remember to connect the movement with the breath, have a stable base and enjoy. Start with 3-5 and you may add up to 10-20 in total. It's entirely up to you.
Try several of these every morning, you will be bendier and stronger in no time. Enjoy!
The picture below shows another version too, this is called a "sun B", it is a bit more strenuous than a sun A, is typically done after several (3-5) sun A's and incorporates a few more asanas as you can see.
Remember to have your breath under control (thru the nose) and to always have a stable base before coming up into a pose. Do not over extend the hamstrings in the forward folds, take it easy! Maybe keep those knees a bit bent, especially in the early am. Have fun!
Debbie Krejci E-RYT 500
Yoga Teacher Training Mexico, Costa Rica, Sri Lanka
become a yoga teacher