I've been doing a bathroom reno this weekend and I found a new product that makes tiling really easy, although slightly more time consuming.
Basically how it works is that you have a little plastic spacer, with the a mouth that goes over the tile. The little orange thing has teeth on it like a zip tie, so once you've got the tile close to being level, you can adjust it slightly and incrementally so that it becomes level, and stays that way (sometimes cement when it dries it shrinks unevenly causing it to not be level)
It makes it easy to have a perfectly level floor and is really easy to use. (I've never tiled a floor before this weekend and I managed to get it perfect first time out)