I actually never realized there was such a thing as an ignore list until reading this thread, so thanks for the awakening! Up to this point I've just manually avoided correspondence with certain types of members. Typically the uninteresting, entitled, or blatantly phishing people are those who I will disregard first. After that, I find it takes a bit more nuance to suss out the seed from the chaff. I don't post on or read these forums much, so I lack a lot of context regarding the character of certain members. In light of that, I find DM's and their subsequent content tend to funnel my focus -- I keep up with and try to talk with the interesting people while the rest seem to fade away.
And oh yeah! If I get one-sentence messages about how my day is going > Trash Bin.