It's difficult to find a guide for fighting crawmerax without cheating. After hours of attempts I beat him using a strategy I made that should work for every character.
Before you go after crawmerax you need a good loadout. Luckily you dont have to run around the map to find stuff thats good enough. There are a few places with several chests that you can search until you find what you need. Also make sure you are on the max level. (69... no seriously)
On level 69 crawmerax will be 3 levels above you. but anywhere below he will be at least 4 levels ahead making him that much tougher.
Anyway, if you beat MINAC in the claptrap dlc, you get rewarded with a room filled with several chests, and if you leave the game and come back, you can open them again!
You need... alot. I'll just list everything.
First of all lets focus on the class mod.
You need a class mod that can regenerate ammo, and increases damage with a SPECIFIC gun. For example, the siren would use a mercenary class mod that has ammo regen... which is rare........ but... with the soldier I had to get 2 class mods. One with increased shotgun damage, and one with ammo regen. when i ran low on ammo I switched mods, and ran around until i got all my ammo back.
The shield... just the most powerful shield you come across. nothing specific.
Grenade mod... doesnt matter. you probably wont use it.
Guns... you want guns that deal more damage with the class mod... meaning all of them will be the same weapon type. but you need the proper elements.
A fire gun, electricity, corrosion, and a gun with high fire rate and damage. I would recommend torgue. (They suck in bl2 but in bl1 they're awesome... but apparently most people don't agree)
After that sell any extra crap you have in your inventory to make room for all the medkits you'll need. Any time you take damage during the fight, use one. Don't bother being conservative.
Dealing with his Minions
This is the first and probably most important step to standing a chance against crawmerax.
He has 3 different types of minions. Craw maggot, green craw worm, and armored craw worm. The only way you can realistically kill any of them, is with their weakness (element).
The craw maggots are weak to electricity, green craw worms are weak to fire, and armored craw worms are weak to corrosion (armored craw worms are the purple ones). Green craw worms wont take much damage unless you hit their eye, meaning your fire gun needs to be pretty accurate. (If you're the soldier using a shotgun, maybe just use a volcano sniper).
Crawmerax will always have 3 minions. If you kill one, another will take its place. Kill them until the only ones left are the armored craw worms (they're the purple ones.) They're also the slowest so you should be able to keep a safe distance from them so you can focus on crawmerax himself.
Dealing with Crawmerax
Once all of his minions are armored craw worms, (see the previous section) you should be able to focus on crawmerax. (while making sure to keep a safe distance from his minions.)
He's fast but try to keep a safe distance. If he gets too close, keep in mind its faster to turn around and run than walk backwards. (though you cant deal damage unless you're looking at him) He has several weak spots and if you hit them enough times, they'll break off.
That's good because it's progress, but it also means you have to be sure to break all of them. The two most important are the eye, and the back.
Be sure to hit the back any chance you get. It's the most difficult to hit because Crawmerax chases you most of the fight, so any time he turns his back to you, get some shots in.
Also try to focus on the eye more than his joints. Once you break his eye he can lose sight of you, sometimes causing him to turn his back to you when he doesn't know where you are.
I would recommend leading him in a circle around the walls of the arena if you can. The last thing you want to do is get cornered.
If he knocks you out try to kill one of his minions to revive (using the element of their weakness) and use a medkit every time you take damage. Yes. Every time. Don't be conservative. 2 hits and you're usually dead.
Once you destroy his eye, focus on the joints. Remember to hit his back whenever you don't have to wait half an hour for him to turn around later.
Repeat this process for a while, and after enough tries hopefully you'll find yourself successful... no promises though.