There are two ways to make French fries. The worst thing you can do for French fries is cook them in oil that's not hot enough. The moisture in the fry can't convert to steam, and the fry will become oil saturated.  

First blanch the fries in 325 degree oil, then removing them, letting them drain, and then finishing them in hotter oil. The point was to cook the fry just until it became limp and floppy, but not greasy. Finishing it in the much hotter oil serves two purposes - besides providing enough heat to brown the potatoes, it was hot enough to make the water inside the potato boil. That water then turned to steam, and pushed out from the inside of the potato, preventing the oil from entering. The result - crispy on the outside, soft on the inside, not greasy. 

There is another way. If you start your French fries in medium-hot oil - around 300- 325 degrees - and remove them when they just become barely floppy, you can drain them, let them cool, and then finish cooking them in a 500-degree oven on a baking sheet, preferably with a draining rack. There will be just enough oil left on the fries from the first cooking to brown up the fries. 
Alton Brown, TVFN