Ok, this is something easy but that many don't know: how to use the Top Keywords tool!
This tool lets you find the 10 Top Keywords used to reach one of your GIGs, considering the impressions, clicks, orders etc etc
There's a lot that can be studied, but the most important thing probably, is that you need:
1) to use those keywords inside the title of your GIG, to increase the impressions
2) doing the same for the tags, BUT (important), to have the best effect you must include (in the tags) keywords not used in the title, so to have a broader effect!