I see a lot of people use Google Scholar and ResearchGate alerts, but I find those alert systems too overwhelming to the point I get inundated and treat them like spam. Perhaps I'm not using them effectively, though (e.g., too many AND operators in my searches). Any tips to improve my experience? Any alternatives that you might suggest? I'm intrigued by ReadCube Papers for its capabilities to integrate searches for papers, citations, and annotations (which is something I've also struggled to do, having used three different pieces of software for those functions), but I'd prefer something that doesn't have a subscription payment structure, at the very least.
Some options, most of which are actually not software:
Subscribe to alerts for new papers published in your favorite journals via email or rss feed. (Be selective enough to not become inundated.)
Try a recommendation engine (and pay with your privacy) like Mendeley.
Subscribe to newsletters of relevant research associations and networks.
Ask colleagues what they've found interesting recently, or more specifically what literature they recommend on a given topic.
One tool that often goes overlooked is the RSS feed. Most journals have RSS feeds that allow you to subscribe to all the new mailings of the journal or just specific topics and headings. Here's an example from the Physical Review journals. You can load these URLs into your favourite RSS feed reader software and then, if you like, further filter them by keyword in your reader for an added level of customization and filtration.
Personally my field is one where new papers are posted to the arXiv. I prefer to subscribe to the arXiv mailings via RSS instead of to the journals themselves. You can also set up separate feeds that filter using different keywords, authors, etc. using the arXiv search API. Here's an example of an RSS feed URL that filters this way:
As an added bonus, you can also keep up with your favourite StackExchange posts via RSS!