I would be careful to not over-engineer your rig. Creating super complex Smart Bone Actions for your character can make for a really cool demo but it's not so useful if the actions prevent you from animating your character to do anything else.
The type of animation you should consider for an SBA is anything you expect to repeat many times throughout your project. For example: eye blinks, head turn, torso turn, hand poses, and mouth shapes.
It's not necessary to automate everything. In fact, a rig that has too much built-in automation is probably going to be too restrictive for actual production use.
Here's one example of an SBA to avoid: A full body turn using a single SBA. This means turning the head, body and limbs all together. This is one that will look impressive in a demonstration but it's not very practical for actual show animation because most character's don't normally turn like that. (Maybe R2D2.)
Tip #1: For Head Turn and Torso Turn SBAs, you might find it easier to animate a single turn and have the animation loop multiple times within a single Head Turn or Torso Turn SBA. If you start the SBA at least one cycle in at frame 1, then you have the flexibility to turn the character more than 360 degrees in either direction. This also means you only need to make the turn once in one direction, not in both directions.
Tip #2: Head Nod SBAs can be tricky. The side view is easy because all you need to do is rotate the head bone to nod the head. But in the 3 qtr and front views, it can get messy if you're not careful.
For example, if you animate the head turn and head nod with entirely point animation, it's almost guaranteed that you will run animation conflicts and get really weird deformations.
You can solve many of these type of conflicts using Multrush's excellent Mixed Smart Bone technique. A search on YouTube will turn this video up. Be sure to watch the first video which explains the technique in detail. The second video is about using a script that automates the setup but, IMO, you should understand how to set this up manually before you rely on the script.
Or, you can avoid the conflicts entirely by separating the X motion (turn) from the Y motions (nod). In other words, only do the X motions in the head turn animation and only the Y motions in the Nod animation. Again, this can be tricky if you limit the animation to Points transforms but you can work around this issue by putting the point animation in one SBA and Layer transforms in the the other...
...or putting a layer transform in one SBA and a group transform in the other...
...or layer or point transform in one SBA and bone transform in the other...
I can go on and on because there are many possibilities for separating the animations to prevent conflicts.
The best approach will depend on the character's design and the way you intend to animate it.
Hope this helps.