Countries: I don't ship internationally but if you're American, you can ship to Puerto Rico, APO, Minor Islands, and Virgin Islands at normal postage rates so you may as well add them. If you're shipping internationally, I'm not sure if you'll want to add everyone or be picky.

Percentage: It depends on how diverse your Haves list is and how much work you want to spend shipping. Right now, I'm only looking to ship ~5 packages per week so my filter is set to 100%. I have a large collection and that's enough to keep cards flowing for me. I'd recommend starting high and then decreasing the percentage to a floor of 75%.

Maximize: Card quantity. I'd rather ship as many cards as possible to get my $TomBux. You might prefer to build smaller packages though in which case you should pick one of the other two options.

Sort: Total value.

Exclude: $1.00 is my limit but only because I can usually use the Window Shopping feature to build a larger package after committing to the cards that show up under my percentage filter. You might want to increase this to get more out of your packages.