I don't know any other manual drivers to ask, so here goes..
Let's say you are making a turn, or taking a curve, and you'll start and end the turn in the same gear. Do you put the car into neutral during the turn at all? Or maybe just put down the clutch to take it out of gear for a few seconds?
That's what I've been habitually doing, I suppose to not lug the engine while I'm putting on the brakes. But I'm wondering if there are better driving habits I should be developing.
Firstly: You'll continue to progress in your relationship with the car so none of this advice may even be applicable in the future. Your shifting is going to be quicker, your sense of how the car reacts at different RPMs will be better, and you'll get comfortable with things like blipping the throttle to downshift, and then getting on brake even as your left foot continues to work the clutch. As you learn how the car works, you'll eventually tolerate a wider range of RPMs. I don't heel-toe.
In GENERAL: Avoid being in neutral. It's annoying and potentially dangerous if you have to change course for any reason and find yourself unable to speed up if needed. Coasting is not the most stable state for the car - you are slowing down, shifting a bit of weight towards the front wheels, and none of the computer-controlled traction control is actually active. For an extreme example of how bad this could be if you really mess things up, look up "lift-off oversteer crash" on youtube. Not the same thing as going into neutral, but the concept is there. You will probably get surprised at some point and find yourself in neutral in a corner somewhere - whatever. It's not the end of the world, just get into gear when able.
As you get better at shifting, you'll naturally downshift prior to corners as needed, and also if you mess up and downshift late, you'll able to do it quickly and smoothly in the corner without jerking the car. Not optimal, but it happens. Don't worry too much about going fast for now.
Additionally, you can let the RPMs fall pretty low before risking stalling (I go down to 1500 in 3rd in my neighborhood regularly), and as long as you're just cruising and lightly accelerating out of the corner (not trying to exit the corner with a ton of throttle), it'll be fine. If it's really slow (like if you get unexpectedly stuck behind a driver who brakes loooooong and hard at every corner), I just carefully downshift mid-corner. In those cases it's not like you're at the limit of car handling or traction anyway, so who cares.
The EXCEPTION for me is turning into super-tight corners, like turning into a parking lot at very low speed. In those I'll make the corner in neutral... sort of. I'll approach in 3rd quickly (say, around 35mph, brake firmly, and then put the shifter into 2nd and keep the clutch pushed in for the 90 degree turn and 7 mph crawl over the bumpy, broken, parking lot threshold. With my clutch is in, I'll come off the brake when appropriate and then just blip the gas, let the clutch out, and drive into the parking lot.
Could I do this by downshifting into 2nd as I approach the parking lot? Sure, but it's annoying. If I downshift early, 2nd gear will be at 4-5000 rpm due to my speed which is a nuisance when doing something as mundane as rolling into a parking lot. If I downshift late, I'll have to brake firmly and complete it before reaching the parking lot, do the downshift while already moving slowly, then potentially have to brake again while entering the corner.
ADDENDUM: I downshift to slow down fairly regularly (especially on looong highway offramps), but I don't get all crazy about it. Some people make it sound like a chant from a cult: "DOWNSHIFTING SAVES YOUR BRAKES." Yeah, except that brakes are meant to be replaced and literally exist for the sole reason of slowing the car down, so use them appropriately. If they were that fragile, then automatics would be totally unreliable pieces of garbage.