The shame of it is that most people will only flag up the bad experiences and very rarely compliment the better organisations.
Some try their hardest to do a proper job (without going over the top) and charge a reasonable rate (remeber the hourly rate is well under half what you are probably paying to have your car serviced).
Find a good manintenance outfit (by reputation - ask for registrations of customers aircraft perhaps and see how satisfied they are). Also, stick to one place so they get to know your aircraft. Don't think it's best to keep moving it around following the cheapest quote.
All organisations should provide quotes for the basic checks with parts and defect rectification/ADs etc charged on top. Keep in touch whilst the work is done and ask to see any offending part that needs replacing.
Some of us are aircraft owners and know only too well the costs involved!