I like looking at the Sports Illustrated swimsuit issue for ideas on posing. I especially like how the models look relaxed, not too posing and really looks like themselves. There makeup looks good too.
Here are some tips:
Bathing suit should be one solid color, maybe golden, red, black, not white, white tends to make a person look bland.
No heavy makeup, especially if shooting outside.
Sunscreen can actually shine your skin so you don’t need to cover your baby in suntan oil, you can protect your skin while you shoot and still look hot and glisten.
Pair jewelry and some strappy shoes or even boots at your shoots.
Catalog style modeling is important to consider, especially for petite models, we tend to want to go very sexy but catalog style that shows energy, personality and action, like playing volleyball is a good idea. The more commercial print looking your photos are they better...even for swimwear.
Look at magazines like Shape, and fitness magazines to also get ideas since on the covers of fitness magazines woman have bathing suits on..
Not just the beach, remember: Lawn chairs, resort looking atmospheres, being in a pool, swimwear can be simple and not dramatic, no crazy backgrounds just simple to make the focus YOU.
Not all tall fashion models have nice bodies, and this is an area that petite models, or shorter models can excel.