Maintaining good slot position will help immensely, but good equipment is key.
And that's why we have a whole thread on mask pr0n. When you rely on your gear, you make sure it's going to protect you when you need it.
I've been hit solidly a number of times, but--and I'm being 100% honest here--none of them hurt as much as when I thought I was cool the first year I was doing LL and didn't have a throat guard (you'll see it abbreviated TG frequently)--not fun getting hit by even a slow foul in the throat. Contrast that with a hight school foul tip straight to the mask from an upper-80s fast ball that was hard enough it broke one of my straps on my TG? Stunned me a bit, but it didn't hurt.