Help and Advice With Wall Before Tiling Advice and information on tiling and fixing tiles to a variety of surfaces

[czucher]

Can someone tell me what do I need to do with these walls before I can tile over them? Can I just use something to fill in all the holes and then just put tiles on it or would I need to somehow take off all the tile adhesive and tat brown layer off before I can put new tiles? Never done this before so any help would be awesome.

Thanks!