Layers Layers Layers

They make things a lot easier to work with, fantastic for organization, and you can hide things behind them.

And for the eyes, I'd suggest looking up how to work with clipping masks in Illustrator. If you do it right, then eyes should be a breeze... so long as you organize your layers then it will be utter chaos.

Cue Discord.

I feel I must say this in response to Emkay's comment...

My Little Photoshop: Clipping Masks are Magic

BASICALLY cause they are. XP They help me tons when I make my space art. :3

You should try Illustrator for Vectoring if you aren't already. It's so weird to me when people use Photoshop.

I use PowerPoint. Because I'm a cheapskate. B)

Don't cut corners.

Also what everyone else said.