Well, there's that whole thing about setting the window-size to be the same as the product of the bandwidth and the round-trip-time; making sure your MTU is as high as possible will help too. This is assuming you've got large, long-living TCP connections that are passing a lot of data.

That's what I know about tuning TCP connections in general... there are *lots* of sites on the web with more information, but a lot of it isn't going to apply because the SE/30 is so slow. Really, the best settings will be the ones that work best, whether they follow "the rules" or not.