I keep track of primer, primer shape, crimps & sometimes size, annulus color, case material, or treatment, as perhaps tinned or copper washed, basic shape (necked, tapered, & etc.) & type (semi-rim, rimless & etc) bullet crimp, bullet shape & material, magnetic or not, & and cannelures on the bullet, plus any colors on the case or bullet.
That said you need to decide how much detail you feel you need to record. Some folk who just collect one case type just draw the headstamp & then note case material / colors & bullet type / material /colors, pretty basic information.
I give this round and description a number, (XXX) & also put the caliber/name in another book. Then if I get another variation of this same case type I write SA (same as) XXX then record this number in another part of this same book under the original number (but the full description is in the 1st book) I have in one place all the numbered rounds of a certain case types. I can look back to the original if needed or find my description of others with perhaps white bullet tips. So two books; one has a list of numbers & descriptions including the formal name (but only on the original entry) The other book has two lists; one the formal name & original number & then the list of other rounds of the same case type filed under the original entry’s number.
This method allows me to put things in the books as I find them & record the case type / name under a number, then if later I find another variation of this case type I can record and then see all the numbers of that case type in one place, should I wish to see if I have a new one or not. With a computers ability to sort this might be a lot easier, so something to consider.
I’m pushing 15K numbered with an easy 25K or so unrecorded at the moment, so it would take me forever to put it all on a computer, but if I was starting I’d be putting it on a computer. However it needs to be one something you can take with you to a show.
I use abbreviations to save space Cu=copper, Br=brass, S=spitzer, Rl=rimless, RR=rebated rim, ba=base, nk=neck, pi=primer, anyhow you get the idea, use whatever, as to how you relate ,and bullet tip colors are written as one color over the other color.
As to headstamp as I use a pencil (with an eraser) & paper I just draw it. I also try to note the shape of “three’s” as sometime they have a flat top or a round top. And watch carefully for spacing and periods or dots in headstamps also the length of dashes may be of import. However you chose to record it just so you can understand it. With a 4 position headstamp how I write in my sale catalogs is: the 12:00 then start from the left and go to the right. (9:00, 6:00 & then 3:00).
Since your collecting MN you will have to note the relationship between the factory code numbers to either the primer or the rim as two countries factorys use 21. & one is written the other way round in relation.
Hope this is of use, best way to however it makes sense to you. your the one who will have to use it so you don’t buy duplicates