Wetsuits serve three purposes as we see it. First and foremost they keep you warm. They can also have the added benefit of protection from the sun and protection from your fins (or the reef).
A wetsuit keeps you warm so that you can have nice long sessions by trapping a thin layer of water between you and your suit. Your body heats up this water. The trapped warm water and the thickness of your suit provide you with a nice layer of insulation. The importance of this is simply that you want a reasonably tight fit with your wetsuit so that as little as possible of the water your body warms up escapes. A baggy wetsuit is bad. (Side note for the guys: getting a wetsuit that way too tight will result in what some call the nut hugger. Also bad.)
There are a variety of wetsuit types from full suits (long sleeve, long leg), spring suits (short sleeve, short leg) to rash guards and a variety of other variations. Choose a suit based primarily on the water temperature. For anything under 68 degrees you really want a full suit. And when in doubt a full suit is the most versatile option. If the water is warmer than 68 degrees where you are surfing a spring suit is a little more flexible and easy to get on and off. A rash guard is NOT designed to keep you warm but does provide protection from your board and from the sun.
Thickness The thickness of wetsuits is measured in millimeters. Often you’ll see the thickness as 3/2 or 5/4/3. All this means is that the thickest part of the wetsuit is 5mm and the thinnest is 3mm. See the temperature guide (link) for how thick a wetsuit you need based on the water temperature where you’ll be surfing. The thicker the wetsuit the warmer and the thinner the wetsuit the more flexible it is. These days the suits are really pretty flexible (especially the premium models).
Construction Wetsuits are made from neoprene of various kinds. All you need to know is that the more expensive suits use a much stretchier neoprene that is a lot more flexible and comfortable. The downside is that these super-stretch wetsuits tend not to last as long. Suits are also stitched and sealed using different technologies. Again, the more expensive suits offer better and more flexible seals which are important mostly when you get into thicker suits. There are also zipper-less wetsuits. Overall, we don’t recommend these suits simple because they are a pain in the ass to get in and out of.
Care Here are two important tips to caring for your wetsuit so that is lasts as long as possible. Rinse your suit off after use in COLD water. Hot water is bad for wetsuits. Second, store your wetsuit out of the sun. If you do these two things you’ll get a much longer life from your suit.
Accessories When you are surfing is really cold water you’ll need booties and gloves. Generally the rule of thumb is to buy booties and gloves that are about the same thickness as the suit you’ll be wearing. Err on the side of thicker for booties and gloves. A hood is good for water colder than 55 degrees. Built-in hoods are nice for those super cold sessions. You might also pick up some thinner booties which are meant for surfing in tropical reef locations. These booties help protect your feet from getting chewed up by the reef.