Assuming you are referring to a standard steel rivet, here is what you need to know:
The diameter of the hole that needs to be drilled for a 1/4 rivet is slightly larger than 1/4, coming in at around 27/64 or 0.4219. This ensures that the shank of the rivet has enough room to fit through without being too snug.
As far as drill bits go, it is recommended that you use a high-speed steel (HSS) twist drill bit with a 118-degree point. This type of bit will give you a clean and precise hole every time. When shopping for your drill bit, just make sure that its diameter matches the size of hole you need to drill (in this case, 27/64).