[header] How to lay tile on concrete [title] Clean the surface of the concrete with a vacuum. [step] Follow up with a detergent, like tri-sodium phosphate (tsp). Make sure the area is well ventilated when you use this strong chemical cleaner. 
[title] Check the levels on the floor to determine if the concrete is level. [step] If it is not level, you will want to purchase self-leveling underlayment to create an even surface.