I listed my iPhone 5 on Craigslist a few hours ago. I received a response and all it said was 'I am interested' and his phone number. Is that how it normally goes?
Craigslist can be awesome, but it requires you being diligent and intelligent.
Here would be my suggested guide:
First, if they try to give you an e-mail to circumvent CL -- just ignore them. CL protects you from future 'phishing' -- i.e. them trying to send deceiving e-mail to get your information. It might seem mundane giving your e-mail out but it opens you up to future risk -- CL e-mail does a great job at being a 'condom' by preventing future unwanted mail. Additionally, for the secondary level of contact I highly suggest setting up a Google voice number to mask your phone number. If you don't know how to do this.... Google it. It connects directly to your phone and gives you a second number, and extra no-cost blocking features.
Second be intelligent about observing and evaluating who you are dealing with. Do they sound like a gangster on the phone? Do they articulate themselves well? Are they respectful (both on the phone and through electronic contact)? I've noticed these aspects correlate strongly with my comfort in actually meeting people. If they are serious about buying, or selling -- they will take the time to provide a serious, mature, respectful response.
Third, always deal locally and in cash (or trade). If they can't do this -- stop contact immediately. It is more than likely a scam. Further, their phone number can provide hints. If they're local they'll more than likely have a local area code. However, just be smart -- if it's not local ask them why? It allows you to get a sample or their communication to evaluate them (see above). Phones use to be a great way to filter scams -- but they have gotten savvy -- so being smart about area codes is a first step.
Fourth, when you do meet - set up a safe and public place to meet -- avoid the temptation to give them a description of yourself or your vehicle. This open you up to being robbed and mugged -- as it lets them know what you will look like when you are still in the parking lot. Just tell them you will call them when you arrive -- and only contact them after you have gotten inside your 'safe spot'. When you pick your safe spot -consider a place with moderate-to-high traffic will help provide you anonymity (for the reasons above). Additionally, consider the value and portability of your item -- can they have a get-a-way car parked a twenty feet away? Malls are great as there are plenty of people to slow them down / stop them, same with traffic -- I met someone at a bank in a low traffic area -- they robbed me outside of the bank and had a car thirty feet away. So I'm drawing this from my own learning experiences.
Lastly, use common sense. I've tried to be thorough above -- but here are many nuances. If you have a friend to bring with you that's excellent when dealing with high value items -- don't let that substitute the above measures. If it's a low value item (<100) it's not likely a concern. The greater the value / portability -- the greater the risk.
I would sum it all up to say that the vast majority of communications you will receive will be scams -- however, once you've made it past those to find real local people -- most people are great.