There are a few underlying principles:
- Pack in a travel backpack, with a separate small daypack and an optional camera bag
- Don't pack too much, keep everything well within carry-on limits
- Make packing and unpacking easy by compartmentalizing
- Wash clothes every day
This is my actual load-out for an upcoming short trip to Central America. It's the distilled result of three medium length (>1 month) trips (to Central and South America, and Southeast Asia), and a variety of shorter trips ( Hawai'i, various places in California and the Eastern US).
The main pack in this load-out weighs 22lbs, including the daypack packed inside. My camera bag weighs 5.5lbs, but that's optional.
I'm male. If you are not, you might want to swap some pants for skirts, or shaving cream for mysterious things that I know nothing about. But you can probably use this as a basic guide anyway.
I consider myself fairly conservative about packing. There's a bunch of stuff here that other travelers may scoff at as unnecessary. This load out can certainly be lightened further, and it wouldn't be hard to get rid of the day pack/main pack distinction and just carry everything all of the time.
I use a travel backpack with hip straps and an internal frame. I've found this to be very comfortable when loaded, and it's fine over terrain that would make a wheelie bag annoying. I like a backpack that zips open all the way, rather than a top-loading pack because it makes my daily packing/unpacking easier. I prefer a separate daypack to one that zips on and off of the travel pack. I've found that the latter are poorly constructed and don't have straps wide enough for my shoulders.
I think my pack is supposedly 2400 cubic inches in the main compartment + 800 cubic inches in the expansion pouch. This is a little too large, and encourages me to pack things I don't need. The expansion zipper is always closed when I leave, but sometimes I buy enough souvenirs that I need to open it on the way back.