Flooring Tile - prep concrete slab for tile?

I plan to tile the concrete slab in a new bathroom in my basement. I hired out the drywall and there is still a bit of a mess on the floor. It's mostly clean, but there are some areas where I can rub or scrape the floor and take up some plaster dust. I am concerned about the bond between the mortar and the slab.

What do I need to do to get this floor in shape for tile. Sand? Mop? How clean do I need to make this floor? A little white "staining" is to be expected, right?

Thanks!

Clean with a scrub brush and hot water. Suck up the mess with a shop vac and repeat until clean. If new plumbing was run under the slab and you have patches, you will need to use a membrane over the floor due to the cold joints created by the slab tear apart and repair.

Thanks. My slab is un-cut and quite level (except a little grinding around the toilet flange). So, I won't need a liner. I will try what you suggest. Hot water and a stiff brush are probably just the ticket.

Thanks again!