I have a simple question. What is the easiest way to model a perfect square starting with one vertex and just extruding that vertex around ?
Presuming the first vertex is selected (in edit mode) :
Alt+R Spins the selected vertices around the 3D cursor
Set : steps = 3, angle = 270 These parameters set the amount of spined vertices (3) and the angle we want = 3 * (360 / 4)... 3 because 3 = 4 minus 1
A A F Deselects the last (A), selects all (A again) and faces them all (F)
This method is better than the other answer (in my opinion), because you set the 3 and 270 parameters once and after that you can repeat Alt+R A A F as you want.
Also, you can make triangles, hexagons, etc... with it (just modify the steps and angle value)
E X 1
E Z 1
E X -1
Select two vertices F
OK, we are in edit mode with a single vertex selected;
E is for extrude the vertex, X is for constraint the extrusion only on the X axis, 1 is for the amount of the extrusion (1 Blender Unit), then press Enter to confirm the extrusion. The same approach can be used for the others two vertices. Then you can select the two unconnected vertices and press F to close the quad, or select all vertices and press F to make also the face of the quad. Anyway, be aware that Blender is not intended to create precision geometry, as CAD systems do.