Maybe I've been lucky, but I have always found the frets to be extremely level. The first thing I do is start lowering the strings at tha bridge, listening for buzz and watching the relief and After getting that action I want I evaluate the nut for height and then apply lubricant when necessary. Then I plug up and set pickup heights to find out how that effects the overall tone. After that I replace the strings. I have found some models might have older strings, in which case I replace them before making my modifications.