Welcome to the forums! As Emill84 stated you can use the search button to locate relevant information.
Here is the link! Cleaning the trackball for noobs.. Pictures included... !! check em out !!!!
P.S. The RIM official fix works when you just want to get it going again. If you lock your phone and depress the trackball and move the ball around WHILE it's depressed it will normally dislodge the debris and your ball will function again. You have to do it a couple of times in different directions.