Please evaluate this statement:

When zeroing an AR-15 using a standard military target (the 8 ½ x 11 with the silhouette and the grid lines over it) at 25 meters, you should put the top of the front site at base of the silhouette. You should adjust the sights so that, when the top of the front sight is at the base of the silhouette, the bullets will strike the center of the silhouette.  This will mean the weapon is sighted in for 300 meters.

Is this correct?

Army's Guide to Zeroing a M4/M16

Yes, but If I recall correctly the sight in targets arent actually 8 1/2 x 11, theyre a little bigger. I can check when I get home tonight. Some people sight in holding center mass but thats all personal preference. The actual targets have directions on how to use them and how your weapon should be set printed right on them.

Ok they are 8 3/4 x 11.5, I dont think it would make a huge difference. I got mine from Law Enforcement Targets Inc. These instructions are for A2 sights, for 600/300 sights I think you have to go 2 clicks above the 300 instead of one.
The instructions on them are:

1. Rotate rear sight elevation knob to the 8/3 setting then up (Right) one click past the 300 mark, for zeroing at 25M

2. Aim at target center, adjust sights to move the shot group as close as possible to the white dot in center of the target.

3. After completion of the 25M zero, rotate the rear sight elevation knob back one click to the 300/800 neter mark, the weapon will now be zeroed for 300M.