While it may be more entertaining to simply rear back and swing, that doesn't mean that a ruler and calculator won't improve your game.
As far as elevation changes go, it's hard to say when it comes to uphill shots, but when it comes to downhill shots, it's pretty simple. With a short club, the ball won't have much forward progress relative to how fast it is falling. The shot could be 30 ft downhill, but with a PW, that will only mean about 4 extra yards. With a 3-iron, though, 30 ft downhill will mean about an extra 15 yards, as it is falling at a slower rate and has a much higher rate of forward progress.
Realize, though, that there are two different types of "uphill" and "downhill." A shot might read as being 3 ft uphill, but if the area in which it will land is downhill, you will want to hit it short, as it will roll a lot more than usual. Similarly, a shot might read as being 2 ft downhill, but if the area on which the ball will land and roll is uphill, you will want to hit it a little harder than normal.
STA 5 is a good example of this. It will tell you that your second shot is 3 ft uphill or whatever, but due to the downhill slope near the hole, you need to hit the ball 6-15 yards short (depending on miscellaneous factors.) STA 2 is the same. The shot is typically 1 ft uphill or so, but your ball is almost always going to roll way too far there (unless you really screw up and leave it 10 yards short.)