I know it is common advice to play in the corners, then the sides and then the center. But, I don't think it is stressed strongly enough. Take a look at this board:
Imagine you are not allowed to play in the pink area, or that points there don't count. Imagine only territory gained on fourth line and below (the yellow, regular board colored area) is worth anything. Think of how much more desperately you would fight for the corners, and how strongly you would lock up the borders so your opponent doesn't sneak into your area. Fight that intensely for the edges of the board before considering the center. That is how important I think this is. Maybe the guideline should be:
Avoid the center! SECURE THE CORNERS AND THEN THE SIDES!! Stay on the 4th line and below until borders are secure! Only run to the center after that!
So, that is "Job #1". Using the thinking above, you still need to make sure you avoid overplay. I understood overplay to mean stretching too far, such that your opponent can punish you, but I didn't have a practical feel for it.
EXAMPLE #1: Here I am pushing hard to try to set the border up around line 12, so that I get a point of territory on line 11 at B11. This is too weak considering none of those stones (A11, B12, C11) are connected to each other or the stones below.
White separates my upper stones with 4 (B10) and I have to go in to damage control.
As you can see - I have no strength and have to reform the border by retreating.
So, here we have the real border after my overplay and the results. The real border is low enough that My highest territory is on line 7, a 4 line loss! I think if I had played B11 as move 3 above I might have been able to claim territory on line 10.
EXAMPLE #2: Same game a few moves later. (Ignore the 19, 20, 21...) Look in the lower left. I was trying to get every last point in the corner, so I did a "double hane", moves A2-B3-C4. This is too greedy. By trying to play right up against my opponent and grab every point, I end up with weak stones that can't stay connected.
White punishes this overplay with the moves below - further reducing my lower left territory.
So, the summary of this post is: Grab and secure as much of the corners and sides as possible, focus on this with a very heightened urgency. Get as much territory as you can around the edges, but with solid moves that don't leave you overextended. If you win the battle around the outside, you should only need to reduce your opponents area in the center and you will be headed for a win.
