Dating sites worked for me because they make it easier to approach, I used to experience anxiety approaching people in real life and that would make me appear awkward or strange. It tends to be easier when you can build up comfort through the internet first.
It's much easier to meet when you know the girl finds you attractive in advance. However most of the women I had success with took the initiative and messaged me first instead of me messaging them. So here's my advice..
Make sure you have yourself together, be the best you can be and present yourself the best way possible, I spent hours researching what a good and interesting profile looks like and how to take pictures.
Remember attractive women get hundreds of messages but most of them are very bad messages, forget the pick up artist lines or asking them how they are, show an actual interest in their profile, their life and what they enjoy. Learn to analyse profiles so you can create interesting questions that require an answer or spark a conversation.
Go in with a positive attitude and don't take rejection personally, the ratio of men to women is much higher and it isn't an indicator of real life. That's why you should work on developing your social skills by joining groups and clubs or by making a real conscious effort to improve your real life interactions as real life is easier if you know what you are doing, most of us with Autism don't but you have to start somewhere...