HeliNate, you would lengthen the linkage to increase pitch.

Shortening it would remove pitch.

If your really interested in truely tweaking the tracking DEAD on perfect, heres a little tip.
This is kinda advanced as you have to be very careful to check to make sure you dont end up with negative pitch in one of the blades.

Instead of adding pitch to the low blade....

Add one half turn pitch to the low blade, and remove one half turn pitch on the high blade. Keep going until they match up. Once youve got them tracking perfectly, make sure to check both blades carefully to make sure that there is NO negative pitch in either blade.

This isnt recommended for most folks because its easy to get negative pitch. But if you want perfect tracking, this is the way to do it.