After filling in all forms and activation of registration try to add some unique features to your profile which will make Your Profile STAND out from others. Emphasise on something that can make it VERY SPECIAL and EYE-CATCHING.
If you want to filter some category of people and thus not to waste time with reading messages from people you sure you won't be interested, use STOP-WORDS. For example if you don't wish to relocate, MENTION it in CAPITAL LETTERS! If your requirements are of specific age group, religion or hobbies (drinking, smoking, diet), again SPECIFY in BOLD AND CAPITAL. Don't waste your and their time!
Try to understand emotional and psychological specifications of women (for men) - they generally are looking for romantic men who will care and protect them, who will make them to feel Very Special. While men in general seek a faithful mature lady who wish to be a supportive partner, attractive (who will beautify herself for her husband, look after one's shape and appearance, i.e. do everything to please husband's eye). And at the same time a lady who will be a wise companion and a good wife and possibly mother.
Don't scare people off with writing too much about your family. Avoid to write about your mistakes in past, negativity and defects. The future will show who is who! However, don't lie and don't lead people on in a wrong direction. Meanwhile try to improve yourself and to live and act accordingly to your new criteria and standards.
Avoid short abrupt answers which may misrepresent you.
Avoid grammatical mistakes (by writing in hurry) unless English is your second language (in this case it will be understood).
When you initiate a contact, don't write too much about yourself (I... I... my...) or too short (it might sounds rude and even silly).
Don't ask for a photo from lady in a direct way. Usually it sounds rude and she may never reply. Be polite - kindly ask for pictures of her place where she lives and of her family. Generally, after such diplomatic ways she will appreciate your delicate manners and will be more open and will send you photos even without you asking.
First letters are very crucial! Try to show your best, it will smooth your correspondence. First impressions are always of utmost importance. Smart quotes will enhance your letters, increase chances for acceptance and add value to your perceived wisdom.
Always CORRECTLY spell the name of The Person whom you correspond with!. Remember Carnegie's golden words: "There is no sweeter sound in the world than the sound of your own name". The same apply to the letters, indeed.
Be accurate with your replies, answer the questions to the best of your ability and in time! Remember to keep contact constantly. Otherwise he/she might lose interest and switch to somebody else (there are thousands profiles on the Internet!)