1. What you're quoted is never what you'll be asked to pay when you arrive- there's always a surprise "hidden" somewhere.
2. If you happen to have gift cards, beware: you cannot use them at the same time as getting a customer loyalty discount. Ever heard of a business that doesn't allow you to use gift cards on a sale item... asking you to pay pre-sale price just because you have gift cards?? (The answer is NO!!). Ridiculous and complete non-sense. Opposite of customer loyalty.
3. A light bulb changed for over $600, only to find out just weeks later it wasn't installed properly. When I took it back, they charged me for it again, and I had to point out to them that it was their own faulty work, so NO, I wasn't going to pay for it twice.
4. If you ever find an error in what you've been charged, don't expect to be reimbursed appropriately or in a timely manner. You'll have to be persistent-- only way you'll get your money back, if you're lucky.
5. Document everything! Quotes, emails, conversations...
AND after all this, you'll walk out made to feel you're the one who is difficult.
Best of luck.