Though I personally have little experience with this so far and i'll probably look like an ass or naive but here are my thoughts regarding this and what i am presonally trying to stick to.
Be yourself, but first you need to figure out who you are. For instance, before i knew who i was, i constantly adapted to the group or person i was talking to or hanging out with. Now that i know who i am, i no longer adapt to others and we don't always agree on everything or see things the same way, but that is how it's supposed to be, we are all induviduals, but by being yourself you will eventualy find or meet like minded people and that will increase your chances of meeting your future partner.
The important thing is to always be who you are, you don't wan't someone liking you for being someone you're not because eventually your true self will show and things will fall apart.
Got any hobbies? try and go to events or meetings that correspond with what you like to do, there's always a chance you'll make new friendships there and that can sometimes lead to something more. (personally still got to put this into action myself)
Like learning new things? Night school or something similar can also help you make new friendships, i think you can never meet or know too many people. (hoping to put this into action next year, would love to learn the Italian language)
Regarding online dating sites... I have some experience with this and it mostly feels like throwing away money, in all honesty there is almost always a 30 to 1 ratio of men to women and women tend to get flooded with private messages and you'll most likely than not, be overlooked, unless you're super attractive and possibly rich.
I had the opportunity to have a sincere talk with one woman on a dating site who was willing to share this information.
Personally i think you still have way better chances of meeting someone in person than online, but you never know.
If you're dealing with social anxiety, all of this gets much harder but from personal experience, pulling yourself out of your comfort zone and facing your anxiety seems to be the only way out. I went from being terrified of asking for directions to now occasionaly starting small talk with total strangers. At first i kept saying stupid shit and being super awkward and horrible at conversations, but the more i made myself suffer through it, the better i got at it and it has gotten much easier.
Hope some of this helps you go in the right direction. One thing i've learned this year is, all things worth doing in life are difficult and take time and effort.