Right, as soon as they call asking you to give them a quote, dont just get the address. Ask what is on the floor at the moment, What is under that, is it chipboard, ply, boards etc. Ask if they have seen the tiles they want.
1, you can start thinking before you get to the job
2, You will have done some research and know your options
3, by asking about tiles it could give you the option of steering them away from B&Q etc and maybe you will be able to supply and make some extra £ that way.
4, turning up at a job for the 1st few times can leave you edgy and nervous. What the client wants to hear is you telling them the best way and the best adhesive to use, not umming and arrring over too many options.
By asking questions about the job while on the phone you will be more prepared and more confident.