For what its worth...
When buying a car, you should make sure the dealer specifically differentiates between the different fees as there are a lot of them and sometimes the descriptions might be vauge. If you are interested, here is a link to a site that explains the fees pretty well:
In a nutshell though, here are the only fees you should have to pay:
[b]Destination Charge - This is a legit charge, however some dealers may try to say the charge is higher than it is. Any online site, even the manufacturers website say what the Destination Charge should be. If your dealer says its different, they are scamming you, you dont want to give them your business. Its worth noting that if you get your quote through a site like Zag or Truecar, the cost already includes Destination. Dont make them make you pay it twice.
[b]Sales Tax - Sales tax is also another obvious thing you cant get out of, but some dealers have found a way to scam you if you have a tradein. If you are trading in a car, they are supposed to subtract the amount they are giving you on the trade-in from the purchase price of the car to calculate tax. So for example, lets say you are buying a $20k car, and they are giving you $10k on the trade-in, and your area has 10% sales tax. In this example, they should charge you 10% of 10k (so $1000 worth of sales tax) as opposed to 10% of the $20k of the new car. A sleazy dealer may try to charge you the full $2k on the sale price of the car, and they'll just pocket the difference without telling you.
[b]Title & Registration Fees - These are mostly unavoidable fees as they pertain to the legal documentation to register the car in your name. These fees vary by state and should be easy to determine by looking online. Once you know what these fees should be for your state, you should expect the dealer to charge you the same. In some states, its cheaper to transfer plates from an old car to a new car than to just get new plates for the new car.
[b]Documentation Fees - This ones a tough one. Doc fees really pertain to the titile and registration process, but is usually listed separately. To me, the time and effort it takes for an office worker at the dealer to fill out documentation should be part of their "cost of doing business". In the past, I've seen this fee usually somewhere between $50 - $100. If you really push the matter, you can probably get them to knock this off, but its so common, I might let it slide if everything else during your purchasing phase is going smoothly. Be careful though of dealers who disguise this fee as something like "Advertising fees" "Wholsesale fees" etc.
Sorry for the long post...but I thought if we're going to discuss "Dealer fees" we should be more specific about which fees we're talking about!