Ceramic tiles

Depends what you mean by floor made good..if you mean made good ready for new tiles,and the floor is solid then remove the tiles and hammer and bolster the old adhesive..so the floor is back to original depth.

If the floor is wooden I would chisel off any loose debris and secure all the nails. Enuring all the surface is flat, lay plywood .

If you are intending on reusing tiles then the grout needs to be removed first, then starting slowly on the first tile gently pry up the first tile, once removed pretty much the same on the rest of the tiles only it will be come much easier. same if not only you don't have to worry if they break. Once removed use a floor scraper and remove all traces of the previous adhesive / thinset mortar. filling and cracks or holes with appropriate filler. Sand down and clean up.

I would remove and if wooden floor I would chisel it off flat and plywood over if on concrete than Chisle of answers screed over

If your floor is wood you will need minimal 6mil ply,if your floor is concrete then it needs self levelling latex

The process should be
Ceramic tile removal
Adhesive scrape and total removal
New base to be cleaned and primed
Latex self levelling compound poured
Depending on product used and or amount of depth poured, a
min of btween 6 to 8 hours to dry prior to flooring with the floor of your choice. However some real wood or glue down lvt priducts may require a humidity test prior to installation to be sure that moisture is at a minimum