If it is rough surf, and the waves are nice and large, go dive the local restaurant instead. Better that than to bash your head on a rock and break your neck. Divers have been killed making large surf entries and exits! Remember if the waves are large, it could be a storm coming in and they may be even, gulp, bigger when you get out!
Dive story, entered in 2-3 foot waves, over rocks (beach ball size or larger), surfaced 1 hour and 40 minutes later with with 4-6 foot waves crashing with force onto the rocks. There wass also the occasional 7 foot swell that translates into, well, you just dont want to be there. It was an interesting exit to say the least and involved body surfing the last wave onto the rocks and then scrambling like hell to get off the rocks before the next set came in. Did I mention the exit was at night? Live to dive another day and make the right choice to avoid the big surf in the first place.
But you will learn that by experience. Experience is recognizing a mistake you made the first time the second time.
That said. If conditions are diveable (remember big surf = big surge. Big Surge= stirred up sand. Stirred up sand = no vis so why go diving?) IMHO Fins off and firmly attached to you, BC empty, Mask on, time the waves. After watching several sets come in you will know the lull when you see it. When the last wave of the set starts in, start your entry, but dont get too far out, just as far as you can safely go into that last wave without it being an issue. After that last wave passes you, move as fast as you possibly can go past the point the waves are breaking and get into water where you can barely touch. This should be well past the surf zone. If you are a 6 foot person, and the waves are breaking in water over 5 feet deep, then you are trying to dive in waves 6 foot or more and should not be there.
When the last wave of the set comes (or one sneaks up on you) Face the waves, turn the body sideways to present the smallest surface area for the wave to hit, and brace yourself, get your center of gravity low by squatting. If the wave will strike you at or above the knees, then you may need to either leap over it, or dive under it. The bigger the wave the more you will need to hug the sand to let the wave pass over you. The wave is most powerful where it is curling over, and immediately after it has broke before the energy has a chance to spread out with the foam. With some waves, there is just no helping it, you are going for a ride. After that, take note of what the conditions were like so you will recognize next time when you should go eat instead of dive.
Crawling is an aceptable exit strategy and in some places (Monestary Beach, Monterey) the only way to exit. But if you have to crawl in, you really should be asking youself why? Why are you risking you life to dive in lousy visibility anyway?