It's always best if you can use a drill press. It will ensure a straight drill, and a perfectly round drill. (provided whatever you're drilling doesn't move while you're drilling)

Use cutting fluid if you're going into metal or aluminum, for the actual drilling, and for the tapping.

A good, general rule of thumb is drill a hole 3/64ths SMALLER than what you intend on tapping. I.e., if you're going to tap a 1/4 thread, drill with a 13/64ths bit.

16/64ths - 3/64ths=13/64ths...you get the picture. Eventually you'll break a bit on your "matched set" and you'll have to size them up the old fashioned way...

For small bores you'll have to look at a chart to see what #6 #8 #10 screws' actual diameter is....

Whatever you do, take you're time. One of the most frustrating parts of tapping is trying to drill out, or remove a broken tap. Especially if it's just the very tip, and it's 1/2 way down the hole....[:@][:@][:@][:@][:@]