The key to crispy tofu is in using the right kind of tofu. It has to be firm or extra firm. Extra firm is best. It also must be thoroughly drained.
I've found the best way to get tofu really dried out is to use refrigeration.
Discard the packaging liquid. Lay the block on a plate layered with thick paper or regular towels. Rest in the fridge uncovered for several hours. Wring out the towels once or twice during the process so they can continue to absorb more moisture. Also turn the block over half way through.
The refrigerator will do most of the drying with its cool, moisture evaporating environment.
Coat a baking sheet with non stick spray. Slice the dried out tofu into 1/2 inch thick slabs. Arrange evenly in a single layer on the sheet. Salt generously. This will further help to dry out the tofu.
Bake at 350 F for 20 minutes, turning over the slices at the halfway point.
Remove from oven. Brush with olive oil and season with additional salt on both sides.
Set broiler to high. Broil the tofu until a crispy, crunchy exterior is formed on the top. About 7 minutes. Turn over and repeat.
Brush with a little more oil after you take them out of the oven. Season with black pepper. Allow to rest for 10 after it's come out of the oven.
The tofu will have a very crunchy, very crisp outer layer and the middle will be tender, yet a little bit chewy. The seasoning and the oil will give the crunchy outer layer lots of flavor. A hint of the oil and seasoning flavor will have penetrated to the center. If you've been successful the tofu will snap like a chip or cracker when you break it or bite into it, but it will have a pleasingly soft and chewy middle.