Bag check - must have things for your tennis bag

Non-greasy type is the best for sports. Some people like the spray type, some prefer the lotion.

Main racket plus backup rackets that should be as similar as possible to the main racket to use in case a string breaks (or to rotate between to make them all last longer).

Lips get very chapped after many hours in the sun, so it's important to use lip block when you're out on the courts a lot.

It's useful to have a towel to dry off during changeovers, especially if you play tournaments.

If you play in official matches, it helps to have a current copy of the "official" rule book for tennis in the US.

It's useful to always have a new can of tennis balls that you can open when playing practice matches. You also want to have some good used balls to hit with when you don't feel the need to open a new can.

In case your grip gets slippery or dirty, it's good to have some extra over grip to use.

Whether you need some change for a parking meter or a snack from a vending machine, it's good to have some spare change in your bag as a backup.

It never hurts to have a pen handy in case you need to exchange contact info or write down some quick notes.

Make sure to always carry water with you. It's important to stay hydrated. Also, once you open it, replace it with a new bottle before long or it will get moldy.

For wrapping fingers in case of blisters, minor cuts, or injury prevention.

You don't want to be stuck out on the court with a runny nose with no tissues.

It doesn't have to be anything fancy. Just some bandaids, maybe some antibiotic ointment, and some gauze should do the trick. Maybe some Tylenol too.

If you're traveling away from home and you break your string, it's much cheaper to get it strung if you have your own strings. Plus sometimes they might not even have your strings in stock.

Shirts and socks tend to get the sweatiest during matches, so it's good to have a clean one to change into after or during the match.