Online dating is certainly one option. I gave it a try a few times and haven't given up on it completely.
Work or volunteer experiences can also (potentially) expose you to a variety of people. If you meet them while engaged in something you care about, that's one thing right off the bat you two would have in common.
They say it's best to increase your activity level to increase the likelihood of meeting a compatible match. Pursue hobbies you enjoy and perhaps it will open other doors for you.
With all of that said...romance tends to find us when we're not looking.

Good luck!