Get rid of the clichés
Try to avoid writing things in your profile which are true of virtually everyone. For example, lots of people say they enjoy seaside walks and a nice meal at a restaurant. Well, of course they do - who doesn't? But by writing something like that, you've wasted the opportunity to write something that is unique about you and which will catch someone's eye.
Check for mistakes in grammar and spelling
Read carefully through what you've written. Yes, it's very superficial to judge someone according to whether they wrote 'their' instead of 'there', but when someone doesn't know you, he or she will judge you on what little information you give them - and you want to try and make as good an initial impression as possible.
Don't overdo the pet hates
The 'pet hate' section is intended to be original and funny, not an opportunity to tell the world what you dislike about your ex-partner.
Don't go for 'liars, cheats, rude, arrogant people, people who don't listen' and so on, because i) it makes you sound angry, and ii) everyone dislikes the people you've described. What does this really say about you (except that you're still hurting)? Instead, write something personal. My pet hates are Sailing By on Radio 4 and people who make a big show of tasting wine in restaurants.
Choose your photo carefully
Upload a photo and make sure it's a good one. You don't need to 'release' the photo to anyone until you feel comfortable, but by uploading a picture you are letting your recommended partners know that you are open to that possibility.
And don't use any old photo you happened to find. Make sure you take lots of photos and choose the one where you look your best. This is important because most of us look better in real life than in photos, so a good photo approximates much better to reality than a bad one.
Don't be too narrow with your search criteria
Make them wide. Be open to the possibility that you could have a relationship with someone who is several years older - or younger - than you, who may be much taller or much shorter than you, who may live in a different city or different country to you, and whose experiences in life may be very different from yours.
At the very least, wide search criteria will allow you to browse through many profiles and to make your decision on whom to contact on the basis of more important criteria than age, height, location etc.