Avoid wearing watches, bracelets, and (if possible) rings. They get in the way of lead and follow. Also, they are dangerous to others you may hit on the floor.
Make sure dresses are short enough that neither you nor your partner will catch the bottom while dancing. Make sure you won’t catch your heel on the back step or your partner won’t step on your dress when you do dips etc. Make sure your pants are hemmed to an appropriate length. Shorten any fringe or ties that may be stepped on.
If doing aerials, lifts, tricks, etc., you shouldn’t have any metal or hard materials that your partner will move across on your costumes. Buttons, studs, buckles, rhinestones, beads, the metal on suspenders can all cause terrible bruising when a person flies across them. If you can’t get rid of the studs, buttons, etc. change your choreography so your partner won’t come into contact with the problem material. For learning new stunts, I recommend men wear a T-shirt or collared Latin practice shirt and sweatpants and that women wear sweatpants and a fitted shirt (so it doesn’t fly up when you are upside down) with ¾ sleeves. (This will protect you and your partner from flesh burns and still allow a good wrist to wrist hold.) Ladies will also appriciate having a collared shirt if they are working on sliding neck drops.
Be aware of how your fabric moves (4 way stretch is best) and slides. For example, you wouldn’t want to attempt the "waterfall” in vinyl pants. The follow would stick to the lead and he could drop her on her head.
Invest in quality shoes.
Salsa gentlemen- if you wear a dress shirt, roll up the sleeves so you partner’s hair won’t catch in your cuff buttons.