Welcome to the forum, Johny.

adsoncraigs (CL autoposter pro) is a good choice, lots of options & updates. But everyone seems to have their own preference. View the stickied thread in the Craigslist section about how to get your ads to stick by UnlimitedPostings. Getting flagged is just part of CL. Even if you post the perfect ad, some a**hole may still flag you simply because he's your competition. It's just something you have to learn to deal with.

And don't be afraid to try out classified ads sites other than CL (backpage, kijiji, etc.)