Start your first lower tiles and pin them up with masonary nails, after using an electrical gauge to source out the wires, copper pipes etc................
The right way start is to batten out...sorry guys but,I'm here to offer advice to new starters not pro's...go with battens and when you dont need them anymore,you have learned your trade well. It took me 4 yrs tiling (without help of any kind) to lose the batten.I'ts all about methods.Tile adhesive application,and choices of adhesive ,given time your action of applying adhesive will be good enough...until then go with what you are happy with,after all a batten will not do any harm....Gaz
Was only 150x150x5 white tiles and used White Star for the first time (good stuff, lovely to apply) and slapped tiles on to datum checked with a level and hey presto, no slippage.