How to check brakes on a pre-trip:

Driver Mills is all I have to say for the most part. Personally we were taught what to say, and what to point at. Luckily when i got my truck home the first time I was able to haul my dad out of the house for a little while so he could teach me what to do, rather than just being a parrot.

 

keepem at a 1" they'll be fine.

 

Auto slack adjusters adjust by brake application.
I have found trailers in the past though that had been probably run on flat ground allot, and with nobody doing a real pretrip.
In these cases I have found trailer brakes well out of adjustment, with auto adjusters that worked. The problem was that the brakes were not applied firmly very often. I had this happen in my first new style road tractor also.
The adjusters worked fine. I had never been told that I needed to pump my brakes now and then when stopped to adjust them. I had always had old trucks that I had to manually adjust my brakes, which I have never had an issue doing.
And I normally was skipping the part of my pretrip where I would pump the brakes. I knew that my valve would pop when it was supposed too, and I knew my air buzzer worked. So I had not bothered. I would hold them to listen for leaks, and see if I lost pressure, but that was it.
To adjust they need you to apply 60-80 lbs of pressure.

 

Up here in Saskatchewan Canada, I was taught for manual slack adjusters. 1 inch of travel if the brake pedal was applied, or 1/2 inch of travel if you're pulling on them by hand is acceptable. For auto adjusters, 2 inch's of travel with pedal application and 1 inch for pulling by hand.

In Saskatchewan the driver is allowed to adjust manual slack adjusters, but only auto ones in a pinch to get it to a licensed mechanic.

I had to adjust my manual slack adjusters on my trailer the other day, it only took 5 minutes. Tighten them down all the way, and back it off a 1/4 turn. Those instructions were straight from a licensed mechanics mouth.

I guess in Ontario only mechanics can touch the brakes. Anyone want to chime in on what the laws are in other province's or states? I only run regional, so I'm not up to date on other places.

 

I don't know if this will help, I have learned the "hard way" how to do brake inspections,(been attempting to drive since 79') please don't think I'm an expert as I am still learning.
First, for your pretrip you should of course check for air leaks, by charging the system with air and all the brakes released with the engine off, regs state that a tractor-trailer system with ten sets of brakes should be no more than three lbs per min leak off. then, I would pull the trailer brake handle down and tie it off with something so it will not release, then do your "walk around" listening for air leaks. I've also found it helpful to "kick" the brake chambers on any new trailer that I'm hooking to because more than once, I've found that they were only hanging by the linkage and the hoses. That would be really embarassing if dot did a level one out on the road on you. regs read if brake assembly affects the brakeing ability by20 percent or more they will put you out of service, in other words, you have six brake assmblys on the tractor and four on the trailer "normally" if one was out of adjustment or defective on the tractor,(less than 20%) they would not put you OOs, just a violation and you could leave.
But in example if one was not working or out of adjustment on the trailer,
(four brake assemblys) that would be more than 20% (25% actually) that would put you OOs with a violation and you would not be allowed to move until it was adjusted or repaired.
Sorry for being so long winded but I hope this helps.