Entering waves in at the start:
The key to making it through waves is to not get caught where the wave crashes, duh! The hard part is knowing when and where to be to avoid it. This is tricky because a wave is moving so you can get pulled into a break that throws you into the crashing white water. Anticipation is key here.
When wave breaks are decently spaced apart take your time to watch the time between breaks. Also watch for where the waves are crashing because they will generally crash in the same general area. They won't always break and crash in exactly same spot so it's good to learn how to read a wave. The best way to learn this is to be around and watch watch waves. (If you don't have the option to watch and practice around waves keep reading and I'll give you some tips.) If you swim like mad between crashes you may make it through without getting tossed. This takes a certain amount of experience and good judgement.
When you can't avoid a breaking wave you'll want to dive into the wave towards the ocean bottom and grab the sand until you feel the wave pass. Then you pop out and swim past the wave to calmer water. It's very important to note that you don't want to get caught right where the waves are crashing. You'll want to dive a little before or a little after it crashes. Otherwise you'll get caught up in it and tossed. If you feel like you're being lifted into a wave even just a little play it safe and dive. It's always safer to dive into the wave rather than to try and swim over it and find out after the fact you couldn't make it ;) Also, you won't always be able to reach the ocean bottom. This is ok, you just want to be moving in the opposite direction of the crashing wave.
Swim safe and let me know if you have any other questions.
If your interested in seeing a few pictures and videos of waves at other races check out these two links:
LA Tri Wave Videos
Straberry Fields Wave Pictures