Traditionally, botanists and hobbyists used plant keys to at least narrow down an identification. Here's an example of one for the NE US: Go Botany plant key. When using a key, you follow a path towards (one hopes) success by answering a series of questions about the plant. These are easier done if the plant is blooming than only in leaf (or twig). A downside of keys is that they're region-specific; it may be difficult to find one for your area (check University sites; horticulture or botany departments may have written their own keys for your area).
There are also sources that allow you to upload photos and get an ID, but I just tried one (PictureThis) and didn't get good results for an uncommon but sold-in-the-nursery-trade plant, so I suspect only the most common plants will be in these databases. Still, they may be helpful.
There are also apps that work similar to the photo-ID applications. Here's one (Plant Snap) that I haven't tried (my phone is only a phone and doesn't use apps).
Finally, if you're stumped on an ID, we're always ready to help here. Just include at least a couple of photos (flower or leaf close up and the plant from a distance so that we can see the form).
I'm glad thatyou're willing to take the trouble to identify things before pulling them - it would make the gardener who planted them very happy to know that their plants are in good hands.