Goggles

What they’re for: keeping water out of the eyes
How to use them: The straps should go directly around the head in line with the eye area. Don’t pull the straps down around the base of the scull, have them too high, or put them over the ears.
How to choose them: Every decent pair of goggles easily come out of the packaging, always try them on BEFORE buying! They need to fit the swimmer’s face. Ensure they feel suction around the eyes when the goggles are pressed to the eye sockets. Leave them on for a minute and turn from side to side, make sure there is no air moving into the goggles, in the pool this will be water coming in! Goggles that have an adjustable nosepiece are helpful for correct fit. Mirrored lenses block the sun’s glare, helpful for outdoor swimming.
Other tips: Goggles should not need to be super tight to keep the water out. They should be worn as loosely as possible for comfort. If goggles are leaking and you have tried tightening them and adjusting the nosepiece to no effect, throw them away and try another pair! They will not magically start fitting better! 

Swim Cap

What it’s for: to keep hair out of the eyes and face and to make the swimmer more streamlined.
How to use it: hold the center fold of the cap in the middle of the forehead and pull the cap from the front of the head to the back (the fold is not meant to go ear-to-ear, but little kids sure look cute with it that way!). Swimmers with long hair should put it in a low pony tail first then wind their hair into a bun and tuck it into the cap, keeping the bulk of their hair closer to the base of the head rather than the top.
How to choose it: New Mark Swim Team will have a team cap (for purchase) that will be silicon, but swimmers always have an option between silicon and latex when purchasing on their own. Silicon caps generally last longer and are more comfortable (they don’t pull the hair). They are also warmer. If it gets too hot, try a latex cap. Latex are perfectly good, and are cheaper. Dry them out after use and keep them flat to make them last longer.

Kickboard

What it’s for: To isolate the legs for focusing on strengthening the kick.
How to use it: New swimmers should hold it with two hands at the bottom (flat) end of the board. This way they can use it with their head down in the water between breathing, making it easier to kick with feet at the surface. Experienced swimmers hold it at the rounded end, laying their arms over the top of the board, and they typically kick with their head out at all times.
How to choose it: All kickboards are pretty much created equal, smaller swimmers should have smaller boards.

Mesh Gear Bag

What it’s for: Carrying swim gear in an easy, portable way that allows it to dry quickly.
How to use it: Some people try to put all their swim gear in there, including their towel and a dry change of clothes, this isn’t really what they are for. The point is to keep all training gear (what is listed above) in this bag and just drop it at the side of the pool to pull things out of as their needed. It gets wet. Keep a separate bag for towels and things that need to stay dry.
How to choose it: For the above reasons, don’t bother getting anything fancy, a simple mesh bag with a draw string top is all that’s needed.

Towel

What it’s for: Drying off after exiting pool

How to choose it: There are plenty of options for towels and every towel will work. Luckily, it's hard to go wrong when purchasing a towel. They're practically impossible to "break," and every towel is guaranteed to dry you off. Think about the how you spend your time in the water, and how you'd prefer to dry off afterwards, and then choose your towel based on those factors. 

You can go with a beach towel, which is larger than traditional towels and are designed to be both a drying mechanism and a blanket for lounging by the water. Cotton and terrycloth towel, which is a soft, absorbent towel found in a wide variety of prints and sizes, and usually cheaper and effective in use. Sports towels, which are small squares of super-absorbent chamois. Their material makes it possible for them to dry swimmers off quickly, and their compact size means they take up hardly any room in gear bags.