Hi hearted,
There are several ways you can improve you speed! Work smart, not fast but as the others say this will come with experience!
Do's,
1, Plan well, even down to where you place your tools, usually when I'm finished with a tool, it goes straight back in to van (i don't want to have to get it back out again
2, Work clean so less mess to clean later.
3, Don't cut one tile at a time, mark a few and do them together
4, place your tiles strategically, your tiles have to go from where ever they are when you arrive on job to on the wall, you don't want to be moving them all the time!!!!
Don'ts
1, Spend too much time marveling at the 1 or 2 tiles you have set, it's good to have quick look now and then though
2, Drop adhesive on the floor, work on your trowling technique!!, personally, I plaster then comb as I find this cleaner and quicker, others do different though
3, Spend too much time talking to customer.