RPing may seem like hard work, but you can really get into and have a lot of fun. Following my suggestions above will help you have a great time, and make others on your RP quickly appreciate you.
Don't be afraid of adding too many details. The more details, the better off the roleplay will be.
No one liners. They do nothing to advance the story. Most people do not like them as they do nothing for the roleplay, unless your thread starter says that one liners is okay, always assume if it is not mentioned that one liners are not permitted.
Don't god mod: god-modding is when you control someone elses character. For example, if you said, "Jane briskly walked into the waiting room at the doctor's office, dragging Jim beside her. Both of them wrinkling their nose at the antiseptic smell. She glanced at the medical posters on the walls, and the magazines by the hard-backed chairs lining the walls. She went, and quickly sat down in one of the uncomfortable plastic chairs, folding her ankles properly. She watched Jim walk up to the pretty nurse at the front desk and talk to her." Here, you are not only controlling the character of Jane, but the the character of Jim. This makes it hard for others to RP, and should almost never be done.