If you’re an outdoorsy person, your chances of meeting other outdoorsy people are greater in cities well-recognized for their outdoor-orientation (e.g., Boulder; Portland, Oregon), which might attract similar, like-minded people.
Likewise, some cities are noted for having a relatively larger percentage of single people.
When looking at an online profile, look for those shared activities that both you and your date enjoy, that may not cost much but allow for interaction and conversation.
Even if you find out you are not compatible, at least you will have spent the time doing something you enjoy.
What should singles be looking for when choosing a city? Be sure to live somewhere with parks or opportunities to hike.