A splotch of mascara falls off the wand onto your newly made-up face.

Dab the end of a Q-tip into some foundation. Making sure not to drag the skin, pat the tip onto the stain with a light, twisting motion. Repeat if necessary, using the other end. Dust over the area with translucent powder. 

You've sneezed before your mascara is dry! Now you look like a raccoon.

Smudged lip liner/lipstick.

If the smudge is really obvious, you'll need to use a cleanser or makeup remover to erase the damage. For precision, use a Q-tip rather than a cotton ball - and above all avoid rubbing! Re-apply foundation to the area in question, dust with powder, then re-apply lipstick. 

Your eye shadow has become all creased and caked.