This article is from the Macintosh for sale FAQ, by Elliotte Rusty Harold firstname.lastname@example.org with numerous contributions by others.
If you're buying at a dealership, don't pay a penny until the
salesperson brings all pieces of what you've paid for out for you
to see. While delivery is sometimes more convenient, it's a lot
safer if you walk out the store with your computer. Too many
disreputable dealers sell stock they don't have, especially of very
popular items. If you must have the computer delivered to you,
insist on a clause in the sales contract specifying that delivery
must be made by a certain date and time or else the full purchase
price shall be immediately refunded. The clause should also
specify that delivery is the responsibility solely of the seller.
It will normally be necessary to cross out (and initial the change)
of a standard clause in the sales contract stating the opposite.
For maximum safety insist that the sales manager also approve that
change in the contract in writing.
Dealers typically pay between 3-5% of the purchase price
(including sales tax) to the credit card company for any purchase
you make on a credit card. Since the margins they'll be getting on
their sale to you are thin enough already, expect that they will
pass the cost of a credit card on to you. If you intend to
purchase your Macintosh on credit and you're not buying mail order,
you're probably better off getting a bank loan or getting a cash
advance on your credit card so that you can give the dealer cash
(or a certified check.) Your interest charges shouldn't be any
higher than if you paid with a credit card in the first place,
(though there won't be any grace payment for repayment) and the
loan or advance charges probably won't be as much as the dealer
would raise prices for a credit sale. Of course if you're buying
by mail you should definitely use a credit card despite any added
expense. Since most mail order companies have higher volume and
lower overhead than independent dealers, the price difference
shouldn't be very far away from the cash price. Some credit cards
offer extended warranties and theft protection on purchases made
with the card. If yours does then the added protection may be
worth the extra money for using a credit card, especially if you're
buying an easily stolen or easily broken item like a Powerbook.