Firstly, the rules for guys and girls are different, although there are always people who try to break that rule. Don't let that be you!
Bring friends to the beach
Everyone looks cooler when they're having a good time with friends. You'll appear more confident and outgoing, and everyone will envy the photos you Instagram and subsequently post to Facebook:
Take your time to find the swimwear that best compliments your body type. People often make the mistake of thinking "swimwear is swimwear" and don't pay it as much attention as regular clothing.
Don't fall into that trap!
Depending on where you live, you may not be able to don your favorite beach outfits as often - but it's worth investing some time (not necessarily loads of money) in picking your swimwear.
Certain designs will look great on some, and not so hot on others - regardless of whether they're purchased from a designer store or your local thrift store.
Accept that.
Don't get so hooked on wearing a certain brand or design when you might look cooler trying something new out.
It's an age-old debate, and one that doesn't really have a definitive answer. As long as you steer clear of the "banana hammock" look, you should be ok.
Board shorts tend to have more variety in the patterns, with funky Hawaiian and Tiki themed shorts proving popular these days.
Asking a girl's opinion is always a good idea too, just not your mom please.
Girls: How much to reveal
There's a huge journey from conservative one-piece to g-string, and whilst it may seem logical that more revealing = sexier, I don't think that's necessarily the case.
From a man's perspective, a good-looking girl will still turn heads no matter what she's wearing, and often going for something that reveals a "teasing" amount of flesh without giving too much is sexier than "over-flaunting".
Secondly, I remember being at a topless beach and, after the first ten minutes, the site of boobs actually becomes... Normal. As a guy, it's a hard thing to get your head around.
The shades
It always amazes me how, a pair of shades that look great on a friend always make me look like Willy Wonka.
Check out what brand they're wearing, and this might help you narrow down your search.