How can a sticker be removed?
the best way i found out till now is to get them of as good as possible with your nails or a plastic-knife (i wouldn't recommend to use metal knifes or razorblades - if you do, be careful to avoid scratching the bricks surface) and then remove the remaining glue with:


pure alcohol or
glass cleaner
cheap hairspay (spray 2-3 seconds from very close distance and then rub of with a piece of cloth) sometimes also does a good job