I personally use pins for a quick basting. One of my favorite things abut QAYG is that I can get to the quilting part really fast, so the pins dont stay long at all. I also tend to quilt each block or section as I make them, rather than making a bunch and doing them at the same time.
If its a larger piece for basting I will use 'dots' of wonder under on both sides of the batting. Just along the edge, so I dont get too much shifting as I go. place the dots and set with a very hot iron. They are small enough (max 1 inch diameter) to place anywhere and not cause bulk or stiffness, and small enough that they dont create a perminant bond, so there is room to adjust as needed.
For small projects, like 4 inch blocks, I dont usually baste at all, just quilt away then cut it down to the size I need.