Image via Drop
This is possibly the most fun part of the process. Deciding what switches you want for the keyboard. Switches fall broadly into these categories.
These are the quietest of the bunch. When modded well they provide a smooth keystroke when actuated.
Some linear switch examples:
Cherry MX black
Cherry MX red
Gateron Yellow
There is a small bump on the stems that results in a small bump when you press the key. The provide great feedback when you are typing.
Some tactile switch examples: