Starting with a reduced charge that is 5% below listed maximum, you can go up in half grain increments, in a 308. For a 223 I go up in increments of 0.2 grains.
A chrony is handy when working up loads. You will see velocities rise with each increase but at the same time the increases will not be regular. That is, velocities do not increase by the same amount for each half grain increase and you will see that that you are not getting much more velocity, for burning more and more powder.
It is around this stage that you could start shooting for group at 100 yards. Three shot groups would do for a start.
At all times you would be watching for pressure signs.
If you are without a chrony just go with 3 shot groups of each load at 100, checking each shot for pressure. As you gain expertise you will be able to set up a chrony and shoot "try-out" loads for group at the same time.
Good luck, mate.