A combination of both is good. If you just blow dry it straight, it comes out a bit frizzy. If you blow dry (use a brush to help when you blow dry it straight) and then use a straightener after, it comes out straight and smooth with very little frizz. That's what I do.

Also, for a straightener, I'd recommend getting one that has a temperature you can set. If you're nervous about frying your hair, you can set it low. For me personally, my hair just doesn't fry at all for some reason which is very good, so I can set my straightener to about 7 out of 10. Good luck!

EDIT: Oh, and I dunno if you'd be in this, but after I do all that, I put a tiny bit of hair spray on a brush and then brush my hair so it stays. It's so little that it's not terrible hairspray hair, but it's just enough to make it stay nice.