Think about what you want to say about yourself. You want to capture the main points that you feel are reflective of your personality and the things you like and dislike. Paint an accurate picture of who you are without telling your entire life story. Use adjectives and other descriptive words and phrases to describe yourself.
Use specifics over generalities. Instead of just saying you like music and sports, list some of your favorite artists or bands and be specific about which sports you enjoy. List specific hobbies you enjoy, places you like to visit and restaurants you frequent.
Be honest. Don't exaggerate on details or try to make yourself appear to be someone you're not. If you decide to meet anyone who reads your profile, they will probably find out if you've lied so it's best to present yourself in a truthful manner from the start.
Create a well-rounded view of yourself. Don't just talk about a couple of areas of your life. People have many different things that help make up who they are, such as personality, hobbies, religious or spiritual beliefs, family, education, career, goals, talents, likes, dislikes, and so forth. Touch briefly on any area that you think is important in helping to show who you are.
Be confident. Although you're not trying to brag or boast, there's no need to criticize yourself or include things that you don't like about yourself. You might not be happy with certain things about yourself but don't focus on the things you view in a negative light. Being negative will most likely turn people away. You want your profile to be warm and inviting.
Avoid trying to answer every question about yourself. Remember, your goal is to show who you are but that doesn't mean you have to try to answer everything you think might arise in the readers' mind. If people have more questions, they can ask you once you're comfortable talking to them.