Slice the potatoes thin, put into frying pan with heated oil or bacon grease. Add other ingredients to taste. I have found a non stick skillet works best for fried potatoes. Also, let them cook for awhile on one side before flipping them. For crispier potatoes, put less in the pan. In a full pan they aren't going to get as crispy.
For vegetarian or vegan, use oil instead of bacon fat