If you're a regular reader of this blog, you probably know that I keep a 12" cast iron skillet in my pantry which is always full of oil for deep frying purposes. Now, in the past I shirked the fancy pants, high-end method of making fries because I thought it was unnecessary. Now, however, I do not. The key to good french fries is frying them twice, first on medium heat, then later on the highest flame you can get. Here's how you do it:
Slice your potato lengthwise. You can slice them thickly or thinly; that's up to you. Then, when you have your sheets, grab a stack three or four (or more if you can) and slice them into strips. These will be your fries.
Next, rinse and dry your strips. Dry them thoroughly so the hot oil doesn't go ballistic when you drop them into the pan. When the fries are somewhat limp, scoop them out of the oil and onto a paper bag. The paper bag will be unfit for the recycling bin after this. Sorry, Planet Earth. Crank the flame up to high, and let the oil come up to temperature.
When the oil is wicked hot, return your fries to it. Here, use your eyes and your nose. They will tell you when your fries are done. When they are crispy and have nice color, pull them out of the oil and immediately salt them. Eat ASAP.
This method will produce very good fries. If you just slice them and throw them into hot oil, you will get an edible product, but the product will also tend to go limp and get soggy.