BigBlueToe

If you have Ortlieb Panniers that are identical left to right, put a big R on the right ones and L on the left.

Make a plan for what goes in which pannier, and try to stick with it. You'll end up spending much less time rummaging around looking for some small item. (Of course, I alter my plan frequently, especially at the beginning of a tour. Usually, after about a week, I've got it figured out. Also, after several tours, my general packing plan is pretty set, and it's only the small details I alter.)

Pack earplugs.

I enjoy tours far more when I don't have to be a certain place by a certain time. Although I like to do a lot of planning (I think it's fun) and usually start a tour with a day-by-day itinerary already planned, I vary it at a drop of a hat. I find an itinerary to be a good starting point, but it seems foolish to be bound by it.

Always have some Ramen in your pannier. It's always nice to start a meal with some Ramen.

Shop at the travel-size rack in grocery and drug stores. Why carry a big bottle of shampoo if you can carry one of those micro versions?

Don't carry tools, spares, etc. for everything that could possibly go wrong. I'm willing to carry things like that if they're light (extra cables, tire boots, a spare bolt or two) but for most things I carry supplies for things that are likely to happen - flats - or things that could possibly occur and could be a real headache. I carry a spare tube and a patch kit, but no spare tire. I carry a couple of spare spokes, some kevlar emergency spokes, and an emergency cassette removal tool. If something happens that I can't fix with my kit, I can always stick out my thumb.