This is the ONLY way to go. Safe, and if the deal doesn't work out, you can take the bank check back and put the cash back into your pocket. Since the check is made out ONLY to the seller, you have a little security from someone else getting it. A money order is similar, but a certified check is the way to go.
What it tells the seller is that a bank is "guarantee funds", so the comfort level is there. The bank takes on the burden of the money being there, in contrast to a personal check that is only paper and doesn't mean the money is necessarily in the account.