Overall lots of great suggestions so far.
Just for basic ideas I would suggest you study the reloading manuals. Lyman is one of my favorites.
Quite often if you look at all of the loads listed some stand out as giving a lower pressure.
The "safest" loads are ones which totally fill the case with powder yet give a very low pressure. Bottom line too much powder simply will not fit into the case.
The most dangerous loads in my opinion are one where two or more charges of powder WILL fit into the case.
Making some good habits to start will be good.
1. Only one container/type of powder allowed on the reloading bench at any time. At first you may only have one type so that makes it easier.
2. Empty cases go mouth down
3. Only filled cases sit mouth up.
4. Once all the cases for a given charge weight are filled do a visual inspection.
5. If I were loading a series of test loads and using say 30.0 grains, 30.5 grains, 31.0 grains, 31.5 grains, 32.0 grains of powder I would prefer to seat bullets in each part of the series before I start charging more cases.
Learn to pay attention to the behavior of your powder scale, how the needle swings when you drop the powder and you will notice if it begins to act oddly. Check the powder scale zero before each use. Personally I would always suggest a balance type scale as ones "only" scale...the electronic ones are getting better but IMHO they are more an experts tool
.
I totally agree about at bare minimum a caliper being needed, an inexpensive 0-1" micrometer could be good as well. I see those on Ebay for $17 shipped and they are a good tool to have. A $17 one would do just fine for any reloading uses. They are more precise than a caliper, maybe not strictly "needed" but a good investment. I am picky on calipers but my uses were for tool and die. My choices of digital calipers would sticker shock most folks LOL.
I would jump on this one right here and you will have a lifetime use tool for $65. No affiliation but it is my brand and a screaming deal for the $$ IMHO.
https://www.ebay.com/itm/13428117683...mis&media=COPY
Bill