buying a suitable backpack

[Richard Willey]

Here is a helpful hint regarding packing for any kind of trip.
Ziplock bags are your friend.

I purchased a box of the large ziplocks.
Almost all of my gear ended up divided into a large number of separate bags.

This served three crucial purposes:

First, the ziplocks can't be beat for waterproofing.  No matter what happens to
your bag, the actual gear stays clean.

Second, the ziplocks make packing/unpacking much easier.
After folding a bunch of stuff into a bag, suckout all of the air prior to
sealing it up.  This does a remarkably good job of compressing your gear down
to the minimum space necessary.

Third, my gear tended to get rather rank.  Being able to isolate some of the
more "nasty" dirty clothes until I could hit a real laundry was very much
appreciated at some points during the trip.