Make plan that has vertex that match the grid I am sorry if this has been asked before, but I couldn't find it. I want to be able to add a plane, and have that plan create a vertex at each grid point as I extrude it. 

When you first add a plane you get a 2x2 plane. (2x2 relevant to the grid). I want to be able to select one edge of this plane and extrude it (or just drag it) to make it bigger, but as I drag it, I want it to make vertex that match the grid so that I can select any square I want to extrude it further. 

This seems like it should be a pretty standard feature, but I can't find how to do it. I ask because I am following this guys video tutorial and it appears that he does it, but he doesn't explain how. I assume he hit a keyboard shortcut. Watch how after the extrudes it a little, he can immediately select points along the edges to extrude futher. Then he does something and seems to make the whole thing red, and it shows all the squares that make up the plane and you can see its vertices. How do you do this?

Thanks!
I think I figured it out. When he does the first 2 extrusions, the only way I was able to do the same was to select the 2 vertices, then hit "e", but left click before dragging. This seems to make it an edge or a cut or something. After that, leaving whatever was already selected, selected, I hit "e" again and then drag it out. I did that on both sides.

This left the vertices that he clicks on the side. However, here you had to do the same thing. Hit "e", left click to finalize the extrusion, then hit "e" again and then drag it out. This allowed it to come out at 90 degree angles. Otherwise it kept it all connected.  

After that, he went to object mode, hit "a", then w->s to subdivide it into equal squares. 

Thanks for the help.