whats the easiest way and how clean does it have to be before installing new

Depends on how much you have to remove and how much thinset or mastic they used.

Get a BullDog or similiar type of tile remover.

The floor needs to be pretty level and clean before laying new tile.

If you have Day Labor in your area just pick up Jose or Hose B

Or get their cousin, Juan or Two

I used one of those cheap air hammers and a widest blade I could find to remove the tile. Air hammer is about $20. Be sure to wear a mask and ventilate the area. It gets dusty in a hurry.

I found a flat head shovel worked best once it's started. catch a corner, and it'll pop up in one piece with a little pressure. Much less dust and mess than shaterring every piece.

bigger hammer????????????????????

extremely dusty job.biggest chipping hammer you can rent with an 4 inch flat blade. all thinset should be removed. i am saying biggest hammer because they are taller and not as rough on the back. get plenty of 5 gallon buckets for your debris and CLOSE your return air vents or you will have dust all thru the house. did i mention this is a extrmely dusty job.

+1

I am a tilesetter,and there is no easy way to remove it,all you can hope for is that whoever laid it didn't know what he was doing and it might come up easy,but alot of the time it's not the tile that's hard to get up,it's the thinset.

+1 on the largest chipping hammer with a wide flat blade.

Sometimes a pointed chisel will work well to help pop up the tile. Also, consider sealing the area with plastic and tape. Open a window and use a box fan to get the dust outside if possible. All the mastic/thinset needs to be removed. Also, consider getting a better air filter for the A/C unit that will capture any dust that gets into the rest of the house.

We have had a few times where the tile would not pop up with a chipping hammer. In this case we roughed up the surface of the tile with a pointed chisel and leveled the floor...this can be a problem in itself due to transition to other floor surfaces nearby.

got 240sq. ft of tile up. now for the thinset. what about a needle scaler or grinder

scaler is allright, but we usually use just the chipping hammer. if the thinset is real thick and tight it will be too tough for the scalers i have tried. a grinder will dust you out of there