1. Search my comment history. You will see all of the ads I've posted. From the ultra conservative to the crazy "code with me maybe" fiasco that got me more hate mail than Hitler, but also got me a lot of work (a lot). I'm not afraid of being different and of standing out. Though this requires a flame suit.
2. Talk about what potential clients want to read about. I always talk about how my focus is on shipping. It really is. I dont stop working until the damn thing is done and out the door. Turns out, that is not very common with programmers these days. They are too busy dreaming of perfect code and arguing with each other about how Go deals with errors. Like I said, talk about what they want to read about (most of them just want to make sure you can and will deliver).
3.Do write a good headline. My best one so far reads "I ship software." Simple. To the point. And will make them read the rest of the ad.
4. Talk rates right there in the ad. Disqualify people right from the start. You dont want to waste time with people looking to under pay you. Plus you will chase away any dreamer who will gladly give you 5% of his made up company in exchange of "just some code." The higher the rates, the less shit you have to deal with. Honestly. I currently charge $100/hour with a minimum of one week of work. Thats $4000 a week if you want to hire me. But you do get someone who delivers. I have no problem getting paid that amount.
5. Make yourself available. Skype, email, phone. Just answer and take time to talk with clients. Let them know you will listen right there on the ad, and then follow through by listening.
6. Offer them a free 30 minute consultation. This helps both sides because it will give you a good chance to feel the client out, and same for them. Chemistry is very important when doing consulting and a free consultation is a great tool to use for that.
Good luck, and get in touch with me through email (in profile) we can always bounce ideas off each other.