You'll be fine. Just keep in mind when you're drilling screw holes that the screw is necessarily going to displace some wood. The harder the wood is, the less it wants to move or compress. When the threads bite in and the shaft follows, there has to be room for that displacement to occur. In hardwoods, you can't expect the shaft to displace much, if anything at all. The wood will fight it. Then the threads will expand the wood, so it needs someplace to go. Disregarding these phenomena will result in a screw that's far too tight, and you risk twisting the head off the screw and leaving the shaft in the hole laughing at you. Resolving that issue isn't any fun.
You can
go by charts, which usually work out fairly well. They've been developed through long experience. Or, you can sorta sight it in by holding the screw behind the bit with a light source behind it.
It's sloppy, but works in a pinch. If you can't see the threads, the bit's too big. If you can see the shaft, the bit's too small.
Finally, it's critical in hardwoods that you lubricate the screw. Some kind of wax - beeswax is best - needs to be applied to the threads. You can also use paraffin, candles, crayons, etc. (not soap). Just don't drive the thing in dry. You're liable to have to invent new cuss words.
