AE: Faster Previews through 1 check box!
I'll be the last person to say that I know it all when it comes to After Effects. I mean really...does anyone???
Anyway, someone showed me a simple check box in AE's preferences that remove an obstacle that many casual AE users don't realize.
You see, with After Effect's RAM preview, the resolution is tied to the comp window size. What this means is that if you change the preview resolution to half but omit to change the size of the comp window to 50%, you have not saved any time. Sounds complicated I know, but believe me that if you change the resolution to half, you want the size to be 50%. Quarter = 25% and so on...

If you go Preferences>Display and check the box that I show below, it will lock the resolution and size together, which guarantees faster previews!

Two other quick keyboard shortcuts. If you have a full size keyboard, the number zero (0) is the keyboard shortcut to engage the RAM preview. On my Mac it is Function-M. Either way, if you hold down the shift key while engaging the RAM preview, you will create a preview of every other frame and again have a faster preview. Play with some comps and experiment on how you can improve your preview time.
Lastly, don't forget to engage OpenGL if you've got a system to utilize it! Here's an entry on it from a ways back.... AE and OpenGL