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One of the best pressure indicators is an increase in the web diameter measured at the base of the case (immediately above the rim or ext. groove). This dimension should not increase at all (or very little) if you are within safe pressures. If you measure a before and after and the web diam. has increased more than .001", that load is too hot. I have found that one firing with a new shell will expand that area around .0005" and then it stays there.
Don't confuse the above measurement with the diameter a little higher on the case. It's not unusual for a case to expand there and still be a safe pressure.
As for the powder increments to increase - this is my opinion and SOP. If the difference in min to max is fairly small, say 1 gr., I see no reason to fool around with .1 gr increases. I will usually go +1/3 to 1/2 gr. at a time. Don't forget that there is a built in safety factor in the reloading manuals. If the difference is greater, as it is with most rifle loads, I will go in 1/4 increments. For example, if there is 4 gr. diff from min to max, I will increase in 1 gr. increments looking for pressure signs all the while. On the other hand I seldom load at the maximum levels, I see no need to, but that's just me. Some folks want to squeeze out that extra 100 fps. I don't find that that yields tighter groups or deader game.
If your goal is to achieve the one most accurate load for that particular bullet/powder combo, then you should probably increase in smaller amounts. The magical amount of powder that yields a well tuned bullet for your gun will seldom be an integral increase in grains.
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