Many profiles are lists of adjectives: “I’m funny, bright, happy, interesting…etc etc.” Prove it!
Let things show through in the way you write the profile, instead of listing them.
So whatever you write, invest time and effort into getting it right. Always use a word processor for your work, then cut and paste it into the site profile or ad (even if answering questions).
Before you start, always read the site guidelines, and any hints and tips. This builds a document which you can edit and reuse if registering with more then one site, and also gives you a spell/grammar checker to avoid mistakes. Be prepared to tweak the profile as you go along, to change your results until you’re getting good matches from people who fit your requirements.
If you like films, talk briefly about your two favorites - and why they are.