Go to CCS ~~> Trading ~~> Crew Companion. Go to your account settings/profile in the top right and make sure your category is set correctly (you'll only have to do this once... I just can't remember if the system is smart enough to automatically figure out your BES the first time you use it). Then go to the home screen and click on "reserves available" or go to the IAH 737 F/O tab and hit "reserves available" from there.

At the top of the reserves screen, obviously check that you're looking at the right base and then you can set the number of days shown to the maximum of 6, but the most important thing is to make sure the button for "Silo/FIFO" is selected. This is the way the schedulers look at the list and is the only way that really matters or is even useful, unless you're trying to figure out some specific data point.

Now, for each day of reserve (differentiated by background color), you've got "the list" sorted first by number of days available (aka "silo"), and then by FIFO (first in, first out) order within each silo. Simply put, FIFO order means that whoever did something most recently gets reset to the bottom of the list (caveat: people on their first day of reserve are generally on the bottom, even below recent workers). By "doing something," I mean any assignment, whether that's a trip, unused short call, field standby, or whatever. Lots of local reserves will pick up SCs in hopes of not being used, and then they'd be reset to the bottom of the list even though they just sat at their house all day.

The important thing to understand about the list is how many people you have above you who would protect/shield you from receiving an assignment you don't want. This can be a tricky game that's played with incomplete information. Realistically, though, you'll be looking at trips and SCs while trying to decide whether or not to pick something up. Trips might be in open time days in advance... but they might also pop up at the last second. SCs generally remain at the same time from day to day (see the short call matrix here), but the silo they're built for can and will change.

As an example, say there are 4 people available in a 1-day silo, and you're #3 on the list out of 5 in the 2-day silo. If there are no open trips that need to be covered, you might get away with going unused on long call that day, because they're probably not going to build 3+ SCs in the 2-day silo (for IAH, they'll probably build 10, but they'll be spread out across all 6 different silos). Different example though: say there's only 1 guy in the 1-day silo and you're #3/5 on the 2-day list, and in open time there are 3 1-day trips and 2 2-day trips. If no lineholders pick anything up, scheduling is going to use the 1-day guy to cover one of the 1-day trips, but then they're going to have to move to people in the 2-day silo to cover those remaining 1-day trips that are open. There are a lot of different ways it can play out, but the idea is to predict the future by matching available reserves to open assignments in order to judge what you might get stuck with, if anything. If it looks like you're definitely going to get something no matter what, then you might as well APU the most desirable one and call it a day. You'll start to recognize the patterns and get pretty good at this pretty quick if you pay even a little attention to it.