Real simple, actually. No load over the max in a reliable manual, using identical components and dimensions. Shooting over a chrony as you approach that listed max will give some additional indictions to the learned. To wit, a specific increment of powder should give a specific increment in velocity. As you approach from "starting" load by increment, you get the opportunity to be able to note that velocity increment. If, as you approach a book max load, the velcoity increment changes dramatically, sometimes increasing, but frequently decreasing or disappearing completely, you have exceeded max load for that combination of components in that chamber.
In a self-loader, (or bolt, lever, or pump rifle) you need only consider the one chamber. Should you seek to explore the functionality of a book max load in a revolver, of course, you must repeat the above process for each chamber of the cylinder.
I'm gonna go with a generalization: "Relatively new to reloading." Maybe stay away from maximum pressure untilyou have enough experience to sort out the bovine excretai on this and other forums, from good, safe practices.
