If you are larger busted look for molded cups, wider straps and more support in the top portion of the swimsuit.
If you are smaller busted look for padded cups and smaller straps (or no straps).
Darker colors at the bottom of the suit with lighter colors at the top will balance you off.
Prints and patterns act as camouflage and can hide a few bumps and bulges.
Also try ruching (pleats and gathers) around the midsection, diagonal color-blocking, wrap tops, sashes and belts
Black is always chic, slimming and versatile, but a lighter or bright color will be cooler and more comfortable.
Try a bright or pastel color that you love or looks good with your skin tone and you will feel cooler in the sun.
Find a designer style you like and seek out a similar look for less.