I have my third car selling through craigslist right now.
If you want to weed out the bullshit, there are two simple things to do. Be clear and precise about these 2 things only, and you will be all set.
1. CASH ONLY, PRICE FIRM - this kills a lot of run around, and helps keep the low ballers away.
2. NO TEXTS OR EMAILS, PHONE CALLS ONLY - this keeps the scammers and tire kickers away. Generally, only people serious about buying your car are willing to call and talk to you. Its just too damn easy for someone to shoot you an email and ask you some bullshit questions. Sure, not a big deal from a guy or two, but you will get inundated with, "Hey, does it start?", "Hey, do the tires hold air?", "Hey, what oil did you use?", "Hey, will you take $10 or trade for an ice cream scoop?" . . . . . . . . . . "
Bold them in your ad, and don't reply to emails or texts. I put it right in my ad that I will not reply to either, that they have to call.
Be very descriptive, too., it saves everyone time and energy. I include too many pictures, list everything that doesn't function 100%, and I list all repairs made in the last 50k miles (and major repairs outside of that range, like timing chains etc, and at what mileage they were replaced).
It helps keep the questions to a minimum, and you'll mostly just get calls for people wanting to set up a time to come take a look.
Goodluck.
ETA: I wouldn't spend money detailing it unless its horrifically filthy. But I clean the cars up as much as my patience allows. Think about it as if you were going to look at it . .