If you have a dslr camera, have you ever adjusted the diopter?
If the answer is no, and you have a hard time nailing exact focus while shooting in manual, check out this quick tip--it just might be a big help! The diopter is a little slide or knob that allows you to adjust what you see through the viewfinder if you don't have 20/20 vision. If you've never adjusted it (or sometimes if it just gets bumped), it can make it difficult to see--almost like watching TV with a pair of glasses from three prescriptions ago. Obviously, that can make it really hard to get your focus where you want it!
The diopter is usually located up by the viewfinder (on my Canon, it's just to the right of the viewfinder). The proper way to adjust the diopter is to look through the viewfinder towards a white wall, and adjust the diopter until the auto-focus points in your viewfinder look as sharp as possible, NOT to look at an object itself and adjust until it is sharp.
So I'm curious--have you ever adjusted your diopter before?