Generally speaking, the best temperature for deep frying stuff is 375 degrees F. If you try to fry stuff at a lower temperature and/or crowd the oil too much, you will wind up with soggy greasy food. However if you have it at the right temperature, the outside will crisp up immediately, preventing the insides of the fries from soaking up too much oil. Personally I'm a big fan of the "fair" or "festival" style fries, which are simply potatoes cut with a french fry cutter with the skins still on, and immediately dropped into hot peanut oil and cooked until brown and crispy. Because the excess starch wasn't removed from them first, they will be browner than the fries you get at McDonalds for example. If you've got the time, you could instead soak the cut fries in cold water, changing it two or three times, to flush out the excess starch.
The biggest factor imo is cooking them in a large enough amount of oil and making sure the oil is at the right temp.
I've heard of some other techniques though too to prepare the fries - one of the more interesting ones called for tossing the freshly cut fries in some sugar and letting them rest in a colander for a while. The sugar will supposedly draw the excess moisture out of the fries just as salt would, and the bit of sugar that remains will help the fries get a nice golden color and crisp up on the exterior.