Overclocking doesn't work like that.. The overclocking capabilities of any piece of hardware can vary greatly. Although in benchmarks we can test that generally speaking a GPU or CPU can have small or large OC headroom, you might get a chip that doesn't. So Overclocking is an individual excercise.
You need to push your clock speed a bit, test for stability. If it passes, push a little bit further. When it fails, you can decide on staying at the latest stable clock speed and be happy with it, or go further via increasing voltage, which is a riskier task if you're inexperienced (you may fry you card, do at your own risk). But the excercise is the same: Increase voltage a bit (when I say "a bit" I MEAN IT), then push clock speeds further, test for stability.
Memory OC works more or less the same.
If I were you I would just stop at the highest stable clock speed and memory speed without touching voltages until you're more experienced with overclocking. And I repeat: Do all this at your own risk.
Cheers!