Since you are a numbers guy, take a while to figure out what your gear ratios are.

Here is Sheldon Brown's Gear Calculator You may have to count the teeth on each gear to get the info you need.

When you have them figured out, you will see that you have three ranges of gears, one for each gear in front. They probably overlap a bit, and mathematically you can see how they are sorted.

Now, with a good mental picture of where your ratios are, you can use the gears. In hilly country, use the low range and shift up and down with your rear gear. When it flattens out a bit, shift up to the middle range and modulate your pedaling speed with the rear. When you really want to boogie, shift into the large front gear and use your rear gears to fine tune your effort.

Hope this helps.