Dependant on the type of adhesive you may be able to steam it of and scrape it with a decorators wall paper stripper. Then let the wall dry out and apply a pre tile primer that can be purched from tile stores such as Topps etc.

Tile adhesive is very strong, it would take a lot of time and effort to sand it down. The best solution is to skim over with bonding creating a nice flat surface; or as an alternative, depending on the strength of the adhesive, is using a good strong scraper. Make sure to PVA the wall before tiling again.

There are a couple of options, it depends on the substrate!
New houses are generally plasterboard walls / partitions and therefore it is easier, cleaner and cheaper to remove tiles with the plasterboard, all you do then is fix new plasterboard and you have a perfect new surface for tile on, depending area I use tile board for showers etc.
Or, if the original tiles were easily removed and left the old tile adhesive you can carefully apply a steamer to the area, this sometimes softens and will aid the removal, a messy option and can compromise the plasterboard.
If you don't want to comb the adhesive on the wall then it will be fine to leave the old adhesive and coat the wall with a PVA sealer, leave to dry and use the old dot and dab method for reapplying the new tiles. This method can be more time consuming but will produce a satisfactory result.
Just read the additional text, if you are tiling the whole wall I would scrape it off, again here you could just steam it, if it was me I would probably re-plaster the wall and then tile it.
It comes back too, “How much work you want to put it, How good of a job to you want at the end”
Personally, sanding it would be a very messy and big job unless you have a powerful belt sander.
Hope this helps.

Don't use pva and dot and dab is NO NO NO in tiling. It's against BS

http://search.wickes.co.uk/search#w=heavy%20duty%20scraper&asug=

In my experience the best way to remove the adhesive is with a wallpaper steamer,It works a treat.

I've found a nice sharp chisel is a good way!!....

Well you can tile directly over it, but would suggest that you remove all the large bits first. You can do this with a scraper until levelish. Then you can tile over it or have the wall skimmed first then tile.

You do not need to sand it down.

Bill
Pipe Dreams Plumbing Services

Remove any loose adhesive with a paint scaper blade, then tile over with new tiling, Coating the wall with unibond can be done, and may help with adhesion for the new adhesive.

you can tile over but can be tricky if you havent done this before the wall needs to be as flat as possible before you start really , skiming it would be the best idea.

hi unfortunately there is no easy way to remove adhesive ..what you need is a lot of elbow grease and a good scraper ...you could use a small kango ..but your likely to damage the wall ...you really do need to get as much as you can off to get a good bed for your new tiles ...the other alternative is to get a plasterer to come and bond the wall for you ..this will cover the old adhesive ..then just prime and tile ...job done

PVa the existing tiles if sound and tile over them leaving them in place.

Scrape off as much as you can
Repair any damaged plasterboard (if any)
Bond it to bring it flush
PVA and tile over
Voila
Hope this helps

It will not be a easy task to remove the old adhesive, you can tile on top of the old one ,but what I am suggesting is to level the walls with tile adhesive or with adhesives with cement in a there composition and not with bonding compounds as it is not water resistant and being a bathroom a good strong support is recommended

You will be fine scraping back the really bad bits and re-tiling with power mix.

Do not put a steamer on the old adhesive as this could blow the plaster beneath.
Warm soapy water. Keep soaking then use a decent scraper. Remember to seal the wall with ova sealer prior to re tiling the wall.
Otherwise the wall will suck the adhesive and tiles won't stick.
Hope all goes well.

Under no circumstances should you PVA under tiles! Never. Scrape the walls down, prime with an acrylic based tile primer, over board with tile backer board ( board comes in 2mm up to 50 mm thickness) . Glued and mechanically fixed to the wall, with either tile adhesive or construction adhesive. Then tile.