Make sure your plain tea set (i got mine from the 99p store!)is clean and dry.
Draw a design onto the set with a sharpie marker. This one was a 'fishy' design as the handles on the teacups were already fin shaped.
Place the set in the oven and slowly heat, this fixes the marker design...you have to heat it very gradually so the ceramics aren't damaged!
This sets been done for ages and hasn't faded at all despite many washes! :) ps. doubt it would be dishwasher safe though.