The floor in my kitchen had two layers of vinyl, the top tiles and the bottom is a sheet. I removed the top layer and am planning on installing new vinyl tiles on top of the vinyl sheet. I check and it is still pretty well attached to the subfloor and is level. However the floor is sticky from the previous tiles (they were self-adhesive). Any tips on prepping the floor in order to install the new tiles? The new ones are also self-adhesive. Thanks.

Since you're just looking for an inexpensive quick fix, just stick the new ones as before.

If on the other hand you want to do the job by the book for good long terms results, you should remove the sheet vinyl along with any 1/4" ply underlayment that is under it. Take them both up in one operation. After prepping the subfloor you will install new underlayment and then the new flooring. This is a must for best rresults especially if you were to select a higher quality floor.

Your old floor I will bet, has a pattern to it, and so it is textured and may also have a slight cushion too. Putting new tiles over that will not last long.

Jaz