Fennyman's guide to getting sex off Craigslist: 1) Don't limit yourself to CE. You put in a little effort, w4m romantic personals, and even platonic ads work just as well for sex;
2a) In CE, focus on the "un-spammy" sections, if they are to your taste. Easiest is m4m, most of the guys are real enough... Or, at least, the expectations on ad replies are so low, you can template a response and send it to 10 ads, and hook yourself up pretty quick;
2b) MW4MW and MW4M are also pretty solid. And many MW4M ads are "please come fuck my wife while I watch"... You have one little annoyance (guy jacking it to you fucking) in exchange for a solid option (and free!);
2c) For those guys who are curious, t4m is about 50-50 whores and real ads, but again very little spam;
3) If you are a straight, go-get-em-no-kinky-shit kinda guy... Well, you gotta POST to m4w. Seriously, if you POST an ad, women will read it. Then, based on the response you get, and checking out some other guys' ads, you can tweak yours until you get a steadier response stream. If you put a solid week into optimizing an ad, 15 mins a day, you will have at least 1-2 responses per day from real chicks, and then it's just down to are any of them attractive/close enough/etc. Work intensive, maybe, but way easier than trying to find the 4 real ads among thousands of spams in w4m.
As others have said, used to be good, now it's overrun. CL has no interest in fixing it, either... Kind of a shame, really. This is the one section of the site that is the least useful but most visited based on publicly available stats.
Oh yeah, and other than that, if you want a good response... You need GREAT photos. Don't take dick pics yourself, hire a real photographer, some will work on a trades basis if you have any skills/contacts. You get pics, they add to their portfolio, or just throw a photo student $20 and get a good headshot/full body/"art nude" set that can be squeezed down under 150k without looking like shit on CL. Oh yeah, and anything (pic, or text) that makes you stand out/catches their eye is good, even if you're silly about it.
But, overall, best bet regardless of what you want as a guy is to POST for it, rather than searching for it, these days. Here's hoping CL finds a way to retain anonymity of personals while blocking/crushing the spammers. But I'm not sure it's possible.