I’ve searched help and the forum for instructions on how to assign tags to a document, and don’t find anything. No doubt it’s there, but it doesn’t show up easily.
So, how do you do it?
Thanks,
E.g. via the Info panel or via the Tags bar (see View > Show Tags).
Thanks, Christian. A more direct way, which I discovered after posting the question, is to type them into the tags bar at the bottom.
I agree the instructions could be more explicit, e.g. under Documentation > Appendix > Tagging.
Yes. They are primarily relevant to using tags after they have been applied.
You can type a new tag in the Tags bar, or create a new group within the Tags group (which will then be available for assignment in the Tags bar).
Thanks, Bill. Two things: [1] The first can be gleaned from the help file, but only by reading very, very carefully. [2] The second sounds like hierarchical tagging is possible, but it appears, if I am not mistaken, that tags and groups in the tags group function on the same level, i.e., apparent hierarchiality is not recognized. [I recognize that I am here commenting with my inquiries about hierarchical tagging on another thread in mind.]
Regards,
Not sure we’ll find that word in the Oxford or any other dictionary any time soon. 
Eric, Tags and groups are logically much the same in DEVONthink.
It is possible to set up hierarchical tags if one creates them under the Tags group. I’m not necessarily recommending that, as the Tags view only provides a flat view, and although the hierarchy is actually presented in the Tags bar, it’s not intuitive and so it’s easy to ‘break’ a proper hierarchy.
Here’s a scenario. In the Tags group, we create a new tag group named ‘A’. Within ‘A’ we create two subgroups, ‘B’ and ‘C’. Within ‘B’ we create two subgroups, '‘D’ and ‘E’. Within ‘C’ we create two subgroups, ‘F’ and ‘G’.
If I tag a document with ‘G’, then select that document and look in the Tags bar, I will see that it is associated with the tags ‘A’, ‘C’ and ‘G’. That’s logically correct.
If you read the user documentation about how to set up group organization for filing your documents in a database, you will see the recommendation that a group should NEVER contain both documents and subgroups. And of course a group with subgroup content should contain two or more subgroups, as there’s no logical reason to have only one subgroup
That’s a good recommendation, but I’ll admit that often I’ll get sloppy and toss new content into the top level of a hierarchical group, promising myself that I’ll get around to properly filing the new content ‘one of these days’. The consequences won’t be too serious, as searches work and See Also will work pretty well, anyway. (But Classify will become confused.)
But breaking that recommendation when doing tagging really screws up the concept and purpose of hierarchical tagging. In the above example, to tag a document with ‘A’ is wrong. To Tag a document with ‘C’ is wrong.
In playing around a bit the only intuitive way I’ve found to try hierarchical tagging is to do it using the Groups & Tags panel, as that actually lets me see the hierarchical structure. The rule that tags should only be assigned at the ‘bottom’ of the hierarchy must also be followed. Never tag a document by a tag group that contains subgroups. Of course, if tagging is done properly, the higher levels of the hierarchy will be automatically assigned, and if the document is selected, the Tags bar will show that.
Thanks for the thoughts on hierarchical tagging – and filing. I’ve never encountered the suggestion that a folder/group should never contain both folders/groups and files/documents. My filing structure has evolved over time. When the list of files in a folder gets too long and confusing, or when I realize that there are several categories of files, I set up subfolders and move files into them. My guess is that subsequently my generally documents go into the subfolders and rarely into the folder.
I’ll have to review my tagging practice to see whether there’s something similar going on in it, i.e., whether it also has been unconsciously consistent with the application of your principle to tagging. Likewise need to look into the extent to which hierarchical tagging is already possible in DEVONthink as it stands. I see what you mean about the Tags view. I’ll have to check out the Groups and Tags panel. I have DEVONthink in List view most of the time, and as near as I can tell, at least with a simple set of tags, the hierarchical structure seems to be accurately represented in the tags group.
I need more experience with DEVONthink. I’m trying to fit the ways of working with other applications and systems that I have settled into over the years into DEVONthink at the get-go. Probably should let my way of working with it evolve, too.
Thanks again. I’ll be returning to your response for guidance and stimulation in thinking about working with tags.
Perhaps not. Perhaps for good reason. But did you understand what I was saying?
Certainly, and made that no-criticism-intended teasing remark after doing a zero-result Google search for it. 
I didn’t mean to be defensive, sjk. Actually, I chuckled a little when I read your post.
Regards,