Let's say someone comes by with an insect that they need us to identify. I can almost say for certain that I won't know what kind of insect it is. I'll ask questions about where it was found, what type of plant it was on, etc. I'll use that information, and look up the most common pests of the plant it was found on. If I need to see an image, I'll do that as well. I can say that most of the time this is a good strategy. It works the same way when people call about insects or plant damage as well. Did I mention plant diseases and other problems? The same goes for them too. Start with the most common problems, and you can't lose.
For example, this past week at the office a man brought in several larvae he found in a house. He said that he had removed a bee hive from the same area the week before. I thought of hive beetles, but I went to ask an agent instead. She did an image search of several other things that it might be, before we tried "hive beetle larva". That's what they turned out to be - the most common pest for that particular situation.
This aphorism is used in medical school, but it applies equally well here: "When you hear hoofbeats, think horses, not zebras." When presented with a simple and a complex solution, the simple one is probably best.