You may start by reading some crack tutorials...then you got an idea what you're about to deal with....use a search engine to find more...
Then get the "tools", learn what they are and what they do...or what YOU can do with them
Personally, I don't recommend starting with SoftIce (for example)
if you're a total newbie...even if SoftIce is great, it can be tricky...
When you feel like you're ready, try out some simple cd-checks
That's enuff for this time
Try this link for some more info
http://cdchecks.cjb.net/