What's the best way to meet other singles for a 45 year old single lady with no kids?

Interact with people by being confident and comfortable in yourself. Observe how people act towards each other by facial expression. Then you'll  notice some people are approachable and some are not.  The ones that are approachable have fun with it either by flirting, laughing, or ask questions like it is a nice day or I cant seem to find what I need to buy.  I don't know about other guys but I always like to help. You never know the guy you helpped might be the guy you fall for.

When I was in that age group,  I attended gallery openings, classical music events and cultural events. There were not a lot of singles at these events, but the ones that were there were the "cream of the crop."  Cycling clubs worked pretty well too. Again few candidates, but really good ones. Step outside your comfort zone.