I use safety pins(I think #1). Never close the pins. Keep them opened in a container. I find the zippers very helpful as you can sit and put the pins in(and remove) and not have to stand at your machine to do this.
go to this website(where I got my zippers):
http://stores.longarmconnection.com/quick-zip-system/
They have a how-to video.
Edited: I just checked out the video and found it very short. Not sure how informative it would be.
Basically, you attach your base zipper to your leaders. Mark the center with permanent marker. Zip on the other half of the zipper and mark its center with the marker. You fold your top in half and mark the center of top and bottom with a pin. Match the pin mark with the mark on your zipper. Pin center to the left, turn and pin center to the other side. This method keeps the fabric smooth. Pin with the fabric on top of zipper edge up to the zipper teeth.
The zipper system on that website comes with very clear instructions.