Apologies. I'm not very good at tagging outside of Touhou, really.
I don't want to throw around words and end up creating a bunch of entirely new tags, especially when there's possibly better descriptions out there. I figured I'd leave extensive tagging to people who are more familiar with that part of the system.
Uhh, what's hard about the system? You can see that it's at least monochrome, it has a suit and a necktie. By adding a single tag, you're limiting the ways this pic can be found to one, so once it falls out of the immediate recent list, there will be almost no way for people to reach and tag it. Don't do that. Always add at least some generic tags to your pics. This holds for your Touhou uploads as well, you regularly upload with nothing but touhou and a character tagged. That gives no way to differentiate it from the other 45K touhou pics we have.
Your modern danbooru is actually quite easy to find tags in. If you search for one you want to tag with, it'll give you a response, and probably recommend a more appropriate one. Go ahead and tag with whatever comes to mind. What a 'more experienced' person will do when they see your redundant tag, they'll get a mod to add an alias so that if anyone uses it in the future, it'll turn into the 'right' tag.