also, while the advisors aren't your enemy, they *are* salespeople. some stores are more aggressive asking for additional services, others just leave it at what you came in for. neither one is perfect. the first guys, you might be spending 500 bucks that you really didn't need to, and the other guys, you might have missed a service that could have saved undue wear on your car (and a future expensive repair bill).
don't be afraid to say, "not today, but if you could note it on the bill, I'll try to get it done over the next little while". some fixes, they already have parts out and it is just smarter to do then, but most are just fluid swaps and such. plus, it then gives you a chance to do your homework. if you get home and realize you didn't need your halogen fluid changed at all because it doesn't exist, then maybe skip that shop next time... maybe you find a better price than the quoted one on a valid service and can try to get a price match... maybe you do homework and realize you should definitely get it done and the price is good, so you can schedule it.
not only isn't the shop the enemy, but they WANT to fix your car right. be-back visits look bad on everyone. so while it might be frustrating to you, they aren't happy about it. some customers get this idea that techs and service departments get off on screwing up your car... they don't. never assume malice where idiocy or human error can be the problem.