Best way to move to crossfire?

Ok, so my second Sapphire HD4830 is on the way and I want to know what's the best way to oc in crossfire. Should I swap the two 4830 and independently OC to max stable, then put them both in for crossfire? Should I run them at the same frequency (as in, if one outperforms the other when OCing, should I downgrade its OC to match the weaker one?) Should I just throw them both in and go for it, and try to dial in a stable OC on the new card?

Any thoughts on the process would be great. I'm a noob when it comes to multi GPU set-ups.

Edit: I suppose I should've specified that on my current card I've flashed my OC settings to the BIOS. That makes my situation a little more unique I guess. I used Riva tuner to dial in my OC settings, and used ATItool to test for stability, and once I was satisfied I flashed it permanently. Sorry for skipping that important part.

I'm thinking that my questions mostly answered themselves, in that I should probably test the new card independently and then crossfire. Unless I'm wrong about that, the only real question I need answered is whether I can run them with different clocks, or should I match the clock speeds. Any help would be appreciated.