I've read probably between 25 to 30 books on handicapping ... however, growing up, without a doubt the best way to make yourself a better handicapper and develop skill was with a publication called National Charts Weekly ... which later became and is now called Simulcast Weekly.
I believe that this was the very first ever issue of the SW ...
These things - and the NCW before them - were like sacred possessions to me. If someone else touched one they were in trouble. Now ... the thing can be bought online and all.
Starting around when I was in 1st grade we got all of the races on tv on our cable and we lived by a new OTB.
It was much later, in about the mid 90's when I started VCR taping every race from every track each week. My grandpa went to the track and bet 7 days a week - and he was under some hardcore orders to bring back and save me a DRF every day. It didn't matter if it was a Feb blizzard on a Tuesday .. he was getting chewed out if he didn't get one.
When you have the old forms, the vcr tapes, and the charts/simulcast weekly .. you have some real developmental steroids.
All you need is a spiral notebook .. you put the date on top of the page and you watch every race and do a write up for it. The main focus on which horses are better or worse than they appear... and to be on the lookout for possible situations where form may improve or decline
Some of the books are excellent - but none of them advocate doing things the best way.
The best way is viciously time consuming and tedious.