1. You must try and fit. Don't buy swimsuit without fitting.
2. Buy darker color swimsuit.
3. Don't try the high leg one for it makes you looking fatter thighs.
4. Ask the salesman to show you some are good to beginners - quality, style...etc.
5. You may need gogles (under water glasses) and swimming cap. But you don't have to buy this moment. For the gogles for indoor and outdoor swimming pool are different. For swimming cap, some swimming classes provides caps to students at free.