Well, filling up your MoBo with all the RAM that you OS can handle is a good idea, but you might be able to get by with the tips in this ARTICLE. There are also some great tips in the FAQ section (to the right of the forum page) on tuning up one's computer and their OS.
Also, System Memory is both physical RAM and Windows Virtual Memory (Page File). The second takes HDD space, and both its settings and also the available HDD space are things to look into.
A lot also depends on the type of camcorder your video is coming from.
If your'e using a format that needs constant rendering (i.e., there is a red line above your clips on the timeline), press Enter often to render your clips.
Some camcorders also produce video in formats that can be very challenging to work with.