Two questions:
Who is supposed to give it away first, the buyer or the seller?
Most of the transactions I've done, the person with the less significant reputation pays first, it is generally a pretty casual exchange.
If you feel a need for a formal set of steps, and it isn't clear who has more reputation I'd probably handle it this way:
- The person paying with cash counts the cash out onto the table
- The person sending the bitcoins verbally states the amount of bitcoins to be sent and the bitcoin address he will send to (I've also written it down as a "receipt" at times)
- The person paying with cash verbally indicates agreement with the stated information (if you're really nervous about it, I suppose you could have them sign the written receipt)
- The bitcoins are sent
- The person receiving the bitcoins verbally confirms that they have received the transaction with an appropriate number of confirmations
- The person receiving the cash counts it again and picks it up
- Both parties to the transaction leave, happy with an issue free and sucessful transaction
In general, I'd advise:
Arrange a meeting time when you won't be in a hurry.
Meet in a public place (not an abandoned building, or a dark alley).
Bring a friend.
Arrive early.
If you're extremely concerned, you can do the following for added security:
- Meet in a place with higher value targets than yourself
- Meet in a place with some level of security (bank, casino, etc)
- Wear a good pair of running shoes. Not sandals or any type of "dress shoe".
- Choose a place to sit and wait that is not close to the nearest exit.
- Have your friend sit and wait near the nearest exit. If the person you are exchanging with tries to "grab and dash", your friend can get between the thief and the exit.
I've engaged in hundreds of face-to-face transactions, and I haven't had a single issue yet. There is, however, always a possibility that you'll encounter a thief (that's true in life even if you aren't trying to exchange bitcoins).
BurtW is referring to a "verify code" that is supplied to you by localbitcoins if you choose to use their "transaction service". If you use that service, localbitcoins will charge the advertiser a fee of 1%. Once the bitcoins are released to you from the transaction service, the verify code becomes useless, so there is no need to worry about "leaving traces".
If you prefer not to use the localbitcoins transaction service, you can simply provide the bitcoin seller with your bitcoin address (from your bitcoin wallet, or that you generated offline when you generated a "paper wallet"). The seller can send directly to the bitcoin address you provide them. In this case you'll want to have a method with you to check and see that the payment has actually been made. This can be done with a laptop computer or a smartphone. If you don't have either one, then you can call someone at home and have them verify for you that the payment has been received.