Choosing the right gear is one of the biggest barriers to entry into gear-rich activities like skiing, climbing and, of course, backpacking. Before you head out on an ambitious backpacking trip, you need to know what size and capacity pack to buy, how to pack it, what to pack and how many cats you can fit in it. OK, maybe that last part isn't important, but even if it was, the gearheads at REI have you covered with this fun, quasi-expert guide. (Click to enlarge it.)