here's a tip that may help you remember the complicated ones such as integrating letters, numbers and characters

pick a song or speech
use one line
substitute numbers for letters, etc

using Abe Lincoln's Gettysburg Address as an example:

Four score and seven years ago

4sc0r3&7y3ar5ag0

or something a tad simpler than that one above

4score&7yrsag0

you get the idea.

good luck!

HTH