Also, races available from the racing secretary, as well as changes of venue and priorities of the trainer.

Basically, as a handicapper you will often benefit from thinking like a trainer. Of course, in order to do that, you have to study how trainers think. I once told a trainer that I knew the move he was making and he looked at me like I was Satan. lol

I had scoped out a trainer move at FL years ago, invilving a cut back to 6furlongs. I made a major bet for a college kid, and then headed to the track bar. The trainer was there cucking down Seagrams, so I go next to him to listen in.
He turned and looked ut at the track and looked surprised, I heard him say, "S***. I thought this a mile. Dsnged horse can't get started for the first 6!"

D'oh!

Yeah, rule 1: Don't assume a trainer is smart.

Rule 2: Don't assume you are, either! lol

Lol- I've witnessed similar events. Trainers are not reliable when touting their horses.

Yes, trainers only know their own horses. Some trainers are really sharp. Some, not so much.