Things allows you to assign keyboard shortcuts to Tags.
- Bring up the tag manager with
⌘⌃T - Notice the little boxes to the right? Click in one and press a key. Tada!
This adds two bindings: if you have a task highlighted and press ⌃+<key>, it'll toggle that tag on and off.
If you are looking at any view, you can press ⌃⌥+<key> and it'll filter that view to that tag.
I tend to not set tons of these, I like keeping my Readline shortcuts. I do use it for three tags: "Essential", which is just that. The One Thing that I need to do that day. I also have bindings for tags I use for Focus level: "$High" and "$Low".
I use the "toggle a tag" feature infrequently now. I typically handle all the tags at once in the inbox at the end of the day… and @culturedcode added the feature where you can select multiple items and press ⌘⇧+T to tag multiple to-dos.
The ⌃⌥+<key> filtering shortcut is still very helpful, but increasingly I lean on using x-callback-urls to build filtered views for certain kinds of tasks.