Before I answer your question, I must apologize, I misread it. Perhaps there is a better phrasing, perhaps I should L2Read, C'est la vie. In any event I will try to answer your question:
When do you make decisions.
I know you asked specifically about the little things, but I don't really consider anything on your list little, and I do it at the same time I make almost every other decision (except micro).
To make it up to you I've decided the theme for this answer will be Green Eggs and Ham. Please begin each title with: I would not eat them...
In a box
The number one thing that triggers a decision for me is that little pop up you get on the left side of the screen every time something finishes. Usually this is because as soon as I start I thing I immediately forget about it as I've moved on to the next thing. That pop up is usually a good reminder of when something has to be done. Ideally I'll catch things right before they're done, but that doesn't always happen. Examples of things are:
- Upgrade finishes -> usually meaning I should start a new upgrade
- Units finish -> crucial for reinforcing a battle or realizing you just hit 5 Muta
- Expo finishes -> I should have already Maynard my Drones, but sometimes I forget, and I'll often throw down Extractors when the expo finishes
Here or there
I spend a lot of time sending scouts at my opponent or sending things around the map, and as I keep one eye on the mini-map every time they run into the enemy this means I'll have to make a decision. Whether its: micro the unit to keep it alive, or rally my forces, or hey, he through down an Armory, this is when a lot of my high level decisions are made. Examples are:
- Did my scout provide new information -> Should I tech switch? Should I attack because he's weak or out of position?
- Not enough information? -> Send another Scout (maybe an Overlord instead of a Zergling or from a new angle)
- Incoming army -> Rally the troops, rebind my hot keys, queue up more units to reinforce, save my scout (in that order)
99% of my time is spent looking at my base (usually my main, but I skip around) thinking about Droning or Teching. If you're spending time looking at your army or parts of the map, chances are you are doing it wrong. Only time you should look at your army is when they're in battle, and only time you need to look at the map is when a scout encounters the enemy. The rest of the time you should be looking at your base. The key things to look at in your base are: What are you getting? What is your supply? What do you need? and Larva. The decisions I make off of this information are things like:
- Should I be expanding?
- Should I be teching? If I could I would get every upgrade in the game. I usually hit 2/2 around 120 supply
- Is this expo almost done?
- How many larva do I have? -> a lot usually means I need to spray again, very little usually means I don't have enough queens/hatcheries
Sam I AM
Even with these useful queues there are still things that fall through the cracks; things like spreading overlords and spreading creep tumors. For these things I don't have good advice for you, they're just things you have to get used to. I often find making an extra Queen just to make creep tumors really helps me remember to spread creep (I usually bind her to her own control group). Sometimes just cycling through your control groups will remind you of something like: need to spread creep for my Hydras, or Why aren't these Muta out harassing? I'll even toss a bunch of overlords on group 7 or 8 just to remind me to spread them out. The hot keys help, but unless you get in the habit of checking these things when you have a spare moment, chances are you'll just miss them.
I hope this helps.