The number one lesson: Avoid the Acronym Alphabet Soup.
In other words, advertise not what you are good at, but what you are great at. It can be quite tempting to list all of your specialties, all of your skills. However, Brilliant Chemistry is not LinkedIn. It’s not oDesk.
When you’re filling out your profile, don’t advertise skills that you’ve spent little time with. Unlike resume and profile sites, you don’t want to list every possible skill you can. Instead, concentrate on what you do well so you can make the most of your time. It is very tempting for an experienced person to list every thing they’ve learned or been exposed to. I know this, personally. It’s a testament to your career and what you’ve achieved. But this isn’t a place to show off. It’s a place to make money in your spare time.
When doing side work, you want to use tools that you’re an expert with. Ones that you’re very familiar with. You don’t want to use things that you’re new to or things that you aren’t as efficient with.
For example, I’m really good with Ruby on Rails. But, I’m also pretty capable with python and a half dozen other languages. But when I want to do side work I’m going to use Ruby because I’m very quick and efficient with that.
Further, list skills that you enjoy. If your day job has you working in Java and you know Java like the back of your hand, you might be tempted to advertise Java as a skill. But opening up a Scala project is like a breath of fresh air to you. In that case, maybe list Scala instead.
The Avid Learner Addendum
Now, maybe your primary goal is not to make money with side work. Maybe your goal is to break into an industry or a new field. In that case, you might choose to put down a skill that you are not an expert in. You would be willing to take the extra time with less familiar skills because you want to add to your experience. You just have to remember that you cannot charge expert rates and you are not going to be able to bill hours for learning.