Oh girrrrrl, I feel you. I may have "white hair," but my entire fam has stick-straight, 1a hair and ADORE the challenge of straightening my unruly, 3a-3b curls. And for shows, I often have to straighten 3c-4b curls and it kills me, but I do it.
If your ends are a mess, get a trim. Bring in your own products and jank. My hairdresser will cowash my hair and scrunch my hair with a curl cloth if I ask and he hardly gets paid anything, so don't stress.
Here's what I do. Obviously, cowash and whatever first, but THEN:
1. Leave-in. Heat, etc. SUCKS the moisture right out of your hair, so get on that. Aussie 3 Minute Miracle is really nice if you need it.
2. Use a heat protectant on your hair when it's wet. Mine's currently AWOL, but I'm sure a little googlin' will send you right to a nice, drugstore protectant.
3. Blow dry your hair straight first, with a paddle brush and the little straightening end on blowdryers that look like a vacuum nozzle. It'll look suck momentarily, but it gives for more hold in the long run.
4. MORE HEAT PROTECTANT. Lather that stuff on.
5. Straighten. Several times over.
6. Anti-frizz serum. (Proclaim Glossing Polish is my all-time fave.)
7. Hairspray. The Herbal Essences straight one with killer hold always worked for me.
8. Keep that hairspray IN YOUR BAG. And a brush, for that matter.
9. Party and avoid humidity.