Should I straighten my hair before I curl it?

I have chemically straightened hair. I usually do straighten before I curl just to make it thinner, but I just got my hair thinned, so it's not too bad (my hair is EXTREMELY think). Also, any hair products I should use? Right now I use Garnier Fructis hairspray. I would appreciate any other advice, as well. Thanks for the help! :)