A few points for you to consider, which i always give customers
make sure they are fixed price quotes and not estimates, and they state wether they include the vat. make sure its on headed paper with a landline number on it. Check the landline number, use it to ring them next time you talk to them, not just the mobile.
make sure the quote details exactly what you are getting, the areas and the specifications. eg railway sleepers - what grade, new or reclaimed, creosted or untreated, softwood or hardwood etc
can they give references, contact numbers for them, photos or let you go and see other work. Go and see the work, you are spending a lot of money, and talk to other people. Do they turn up regualarly, do they turn up on time? Do they clear up at the end of the day? do they take their boots off if they come in the house? do they charge for every little extra?
do they walk around ffiing and blinding? were there any problems. If you speak to someone ask to go and see the the work theyve done, you could be speaking to his wife or aunty for all you know!
ask how they intend to bed the slabs, check the manufacturers website for instuctions on the slabs your getting (various slabs have different recomendations.
ask about the order of work, when they are starting, how long it will take, and if they are commited to your job only. Ask how many will be working on it, to give some idea of the timescale. Having said that a one man band can do a job better and quicker than a larger company that employs a couple of oickes. Ask their hours of working.
Dont be swayed by membership of trade associations, it doesnt always mean a lot.
Getting a feeling for the people that come to see you. Is it an estimator or is it the gut that will actually carry out the work. I see my customers personally, and carry out a lot of the work myself. That seems to reflect well in the feedback i get from customers, when they accept my quotes. Is it the sort of person you can reason with if there is a problem or do you feel intimidated.
on a larger job i ask for deposit on the day i commence work, usually in the form of a cheque. its normally only enough to cover a few days work, and the cost of the skip, but it proves to me people are capable of writing a cheque, but it proves to them that i have done some work and im serious about the job when i turn up on site with all the kit and start things moving. Be a bit wary of someone who asks for a large cheque before thye even turn up.
ask how they would resolve or rectify any problems, during or after the work. Better to know now than when the problems occur.
Ask how they want payment and at what stages, and agree it in advance.
Ask how they will carry out certain aspects of the work, ie if theres a manhole cover in the way, ask them how they will deal with it. Ask about the height of the paving next to the house ion relation to the damp proof course. How will the slabs be grouted?
consider theyre avaliability. If they can start next week, why? This is the busiest time of the year and im booked out until mid september now, if they cant start for a while, why are they not getting any jobs?
I hope that gives you a guide