How did we learn to use all of the effects? Easy, we read the book. You know, the book that explains how every parameter of every effect works.
What? You don't know about the book? Well, you own it. It's on your AE installation CD. Just pop it into your hard drive and navigate to the \AE6 Documentation\English folder. The book is an Adobe Acrobat file called help_effects.pdf. We recommend that you print it out, take it to a stationary shop, and pay a couple of bucks to have it bound. It may just prove to be the most valuable AE book you own.
Among its other virtues, this is the only book that explains, in detail, how to use the five free ( awesome ) effects you downloaded when you registered your copy of AE at Adobe.com. You did download the free effects, didn't you? If not, reregister AE so you can grab them. You don't want to miss out on the fun of Card Wipe, Card Dance, Foam, Caustics, and Wave World.
After printing the effects book, you might also want to print the Keylight and 3D Assistants' manuals, which are also on the installation CD.
If you're missing your install CD, you can download the AE 5.5 version of the effects books, which is almost exactly the same as the AE 6 book. Pick it up here: http://www.adobe.com/products/aftereffects/zip/ae_effects_pdfs.zip.