Clothes make the man, so don't always appear in front of friends of the opposite sex in a sloppy way. Learn to dress yourself up. Even if you can't dress up, you should tidy yourself up neatly and look energetic, so that your image will be good in the eyes of others.
Single dog is called single dog because she has been alone for a long time. Therefore, you should make more new friends and attend more friends' parties. Don't stay at home all day, or people will always find various reasons to shirk when they tell you to go out. If you don't go once or twice, people may call you again. More times, people will think that you won't go anyway, and over time you won't ask you out to play again.
If you feel that there is no suitable person around you, then go somewhere else. After all, the world is so big, there will always be someone suitable for you.