What can be done about tagging for low-rep users?
I had a question about xero, and wasn't able to tag it appropriately, or use a "retag-this-please" style tag (anime stack exchange has one IIRC).
We don't want people who aren't well-versed with how Stack Exchange works making tags willy-nilly.
The general guidance is to use the closest tag you can and include text in your question asking for the tag to be created. A user with sufficient privileges can take care of that and remove the text at the same time.
Of course, one hopes that the lack of an existing tag would give would-be tag creators pause before creating questions that are off-topic. In this case it's more an indication that there aren't people asking or answering questions about that app, which is it's own sort of warning.