Here is what I tell people to do. Please don't be offended if I state the obvious, you would be surprised and horrified at some of the ways we have seen comics shipped to us.
1. Make sure all comics are bagged and boarded. I recommend not using modern sized bags and boards. They do not provide enough protection to edges and corners because they are too small.
2. Stack your comics no higher than 2 inches and place them securely (So the do not slide) between two pieces of cardboard. The cardboard should be on the top and bottom like a comic book version of an oreo cookie. The pieces of cardboard should be longer and wider thank the comics buy at least 1/4 -1/2 inch. In order words, the edges of the comics should not extend beyond the edges of the cardboard.
4. When the stack is secure, bubblewrap the stack of comics and cardboard. The bubble wrap should be firmly wrapped around the stack but not so firm as to crush the comics.