painted mugs : sharpies arent diswasher safe.choose PorcelainPEN. Make little dots for orientation. Small mistakes can be fixed by simply scratching off the paint with your finger nails. If you have bigger accidents, remove the paint using nail polish remover. Let dry at least 4 hours. Then put your mugs in the oven and bake for 90 minutes at 320°F to set the paint.
After being tortured by seeing all the "diy plates" with sharpies, I feel honor bound to post that you really should be using a Pebeo Porcelaine 150 pen. Seriously, this is what we use and sell at work-- don't use sharpies people!
DIY: Using Porcelain Paint Pens - don't feel you have to be an artist to be able to make beautifully decorated china with porcelain paint pens - take a look to see what kinds of interesting designs you can make using simple shapes and doodles!