I've wasted the whole afternoon trying to figure out where i'm going wrong with the first tutorial on building a room.

Really annoyed with myself because I can't figure this out. It involves inserting edge loops to make the corner and snapping the vertices to other vertices.

I have managed it, but can repeatedly get it right, I keep ending up with different (wrong) outcomes like this...



What are the correct key/mouse buttons.

I seem to have tried all option, of clicking, holding and dragging I can think of.

I'm using 2009 if it makes a difference.