That's an old, old, old trick. My father taught it to me back in 1965 or so when I was 10. It's great for retrieving that dropped part that falls into a hard to reach spot too.
Just rub the tip of a screwdriver across a magnet a few times and it will pick up most small parts. The stronger the magnet you run across the stronger the screwdriver will be magnetized.
If you want to minimize lost parts put a magnet in a small metal dish (like an altoid tin) and drop your screws in there, they will stay put.
And if you want a really strong magnet, take apart an old computer hard drive. There's usually 1 or 2 really strong ones in there.