I like the glue idea.
The trouble I have with pinning - even at right angles to the seam, is that it can sometimes move the fabric a tiny bit and distort the join.
When I join the rows in my OBWs, I'v started using little appliqué pins. I stick pin straight through the points of the triangles (leave them poking up) then as I'm sewing, just before the pin reaches my foot, I take it out. That way there's no distortion and I can pretty much whip the pins out with my right hand only slowing down rather than stopping completely the machine. Hope that makes sense! :D
In normal piecing, I don't pin square patches (4p, 9p etc) but do the seam nestling thing. For HSTs and pointy things, I pin vertically as Ninnie shows. I haven't tried my OBW stick pinning method on regular blocks yet. And I'm very naughty with borders - just slapping them on, no pins! Which is why I guess they're always waving at me! I MUST start pinning from the centre out, like Marcia says! :D