You should stretch every day, but never stretch cold muscles!!! Do at least a 5 minute warm-up before you stretch. Your heart rate needs to be up to at least 100 beats per minute. You can stretch after a hot shower, warm bath, or a dip in the hot tub.
Make stretching a priority in your practices. If it’s just you and your partner practicing, start your rehearsal dancing simply to a couple of fast songs (shag, milonga, samba, cha-cha, Viennese waltz, and salsa brava) to get your heart rates up. Then stretch before moving into whatever you plan to work on. At the end of your practice, dance to a few songs you enjoy. Then stretch some more. Your muscles are usually warmest at the end of your practice. Therefore, this is usually the most effective time to stretch. I recommend incorporating partner stretches into your stretching routine.
If you are in a group and the leader/instructor/captain routinely begins your practices or classes with cold stretching, pull him or her aside and ask them if they can incorporate a warm-up into the lesson/rehearsal before the stretching. If they are not receptive to this, it is your responsibility to warm-up on your own before the stretching begins. Encourage your friends from the group to join you in your warm-up.
Never perform cold. Find another room or spot off-stage to warm-up and stretch before performances/competitions. Make sure you stay warm until it’s your turn on the floor.