Don't bother... they have huge markup amounts and they are no better than many aftermarket products.
I know, cuz I used to work for a dealership and sell them!
If you want rust protection, I suggest Walmart's rust proofing. I got my truck done there and it was carefully done.
They will also try to sell you paint sealant... don't bother.. if you want something to protect your paint from UV, etc, try one of the aftermarket parts shops.
They may also try to sell you upholstery protection... just buy a can of Scotchguard and do it yourself.
Another thing they may try to sell you is an extended warranty. These also have HUGE profits built in and are usually not worth it. If you want protection (insurance) after the standard manufacturer's warranty, I'd suggest you save a bit of cash each month and in a savings account and then you'll have the cash to pay for repairs after the warranty runs out.
The only exception to the above is if you finance or lease the vehicle for 3 years... a typical warranty is 3/60, that is 60,000 kms and leases may run 72, 000 kms. You can buy the add-on warranty for the additional 12,000 for low cost.
Another thing they may try to sell you is insurance on the payment. If you die, the insurance pays the payments. This is simple life insurance and when you buy it from a dealer is VERY expensive. I suggest if you want additional coverage for this, buy a cheap term policy from your insurance broker.
Finally, often a dealer will offer 0% or 1% or very low interest rates on some cars. These can often be very good deals, because they will be lower than what a bank will charge. But if you are getting standard financing from the dealewr, check your bank rate... it almost always is cheaper.
Oh yes, you can sometimes negotiate the admin fee as well.
Good luck!