You also need to know about Climb Milling vs Conventional Milling. It does make a difference. I only ever use Climb milling unless the part is very rough even then switch back to Climb when it's cleaned up.
Here (about 3/4 of the way down)
http://en.wikipedia.org/wiki/Milling_cutter
In the end it is all down to trial and error. Bad things that require correction include:
-Smoke comming from the machine.
-Parts flying across the shop.
-End mills snapping in half.
-Aluminium "welding" itself to your tool.
-Screaming noises from the cutter.
What I like to do is feed the table manualy and see how it "feels". I then program the beast to go at that feedrate with that depth of cut. Generaly I use a depth of less than half the diameter of the cutter with a stepover of between 50 and 75 percent. But, that's for pocketing and the like. Edge milling I always go easy- I hate tool deflection.
Oh, and don't clean dem chips up with an air line, tempting as it may be, you'll find them everywhere including in bits of your machine that you don't want them to be along with an expensive repair bill.
[Edit]Just re- read that and it sounded a little tounge in cheek so I thought I'd add Safety: if you machine too hard or fast things have a tendency to go wrong and human flesh is a lot softer than aluminium or your HSS cutter- always think safety! [Edit]