Buying or selling anything of value on craigslist can be terrifying because bad people can steal your money or property. But one simple piece of advice can make buying or selling expensive things a million times safer:
Meet in a bank lobby.
Being in a bank takes care of the cash problem. You don't have to carry a huge wad of bills in or out of the branch. Neither does your counterpart. You can either withdraw at the counter or the ATM, and simultaneously have the cash confirmed as real and deposit it to an account. That's a big deal when dealing with high value items like a laptop, tablet, or decent phone.
The bank setting also alleviates secondary concerns, like being intimidated into accepting worse-than-promised gear, or a lower-than-discussed price. Most people aren't going to be nuts enough to get violent in a bank. And you'll also probably have access to an outlet in case you need to plug in and power on any gear that's "just out of battery."
Big purchases and sales still come with a massive dose of caveat emptor/venditor, but going in knowing your meeting place is totally secure will be a huge load off your mind.
Note: Of course, in addition to that, you're going to want to take all of the precautions that a normal, sensible human being would: check out the goods in photos beforehand; if you're buying a computer or other electronic device, insist on booting up, checking specs, etc. But those are very obvious, and don't address everyone's real, secret fear on craigslist. Namely, someone beating you up and stealing your phone or your money.