I am going to lay new ceramic tile on a concrete floor. Is there anything special I need to do to prime or clean the concrete first?

It was carpeted originally, the carpet is coming out along with the tack boards and padding. after scraping and vacuuming I plan on cleaning it well with an abrasive pad on an industrial floor buffer but am not sure the best product to use to clean the concrete that won't interfere with the adhesion of the thinset. Also, should the concrete be primed prior to mudding? Concrete is porous so am concerned it will wick the moisture out of the thinset too quickly, causing it to crack.

Two more things, since I thought of them,

I have never seen a completely level concrete floor, especially one poured with the intention of laying carpet over it, condo builders aren't that particular. How thick can I go with the thinset to level out a "low" spot.

Also, the tile manufacturer recommends 1/2" standard thickness with the thinset, square notched trowel. This sounds extreme. I have heard 1/4" V-notched is better.

Suggestions? THANKS!