How do you "tether" your iPhone to your laptop?

Here is a very good tutorial from Lifehacker. It requires jailbreaking and all that jazz, but it’s really not that difficult.

Word of advice be very careful while tethering with your iPhone. AT&T has tethering for blackberries but not for iPhones. Just because it says “unlimited data plan” doesn’t mean truly unlimited. After a certain amount of data is downloaded and uploaded over their service they will charge you a fee which is alot of money.

You don’t, because it’s prohibited by your terms of service with AT&T and if they catch you doing it, they’ll charge you a penalty or close your account.