Nope. None of the above. All that is Secondary.
Primary thing, first thing, absolute most important thing to do absolutely first... (iiSlashr had the right idea)
READ.
Everything and anything concerning OC of a gpu, your gpu, any gpu. The theory is all the same, particulars change according to the specific card. Videos, forums, Google, all of it. And when you've covered everything, start over since things you skimped over before will now make sense.
By then you'll know exactly what turtlerig is talking about, what software you'll need, what to do or not do with power limits vs voltage changes, you'll understand differences in vram, VRM's, particular cards limitations etc.