It's happened to all of us at one time or another. You're either building something or repairing something. You admire that fine, expensive piece of oak or walnut while assembling the project. You've put hours into crafting, sanding, and dry-fitting it together.
And then it happens. As you put in that last screw, the board cracks along the grain.
Well, it didn't have to happen. It's too late to save that little catastrophe, but you can take a deep breath, back up a step, and make it work. And not worry about another crack.
Here's the trick: before putting in a screw, take time to drill a pilot hole. It should be as wide as the diameter of the body of the screw, excluding threads. This way, you'll still get all the holding power of the screw but avoid exerting so much lateral pressure as to cause the grain to split.
The final thing to do before screwing it in is to rub a bit of bar soap on the threads; one side is enough. This will not only make the screw easier to install: if you ever need to remove it, it will be much less trouble.