Pirate campaign

[Roland St. Jude]

My quick advice for an evil campaign is to get an out-of-character agreement from all the players that they'll work together toward a common end, and while they can be evil, they don't do blatantly evil things to each other. If they all worship the common god, that provides a good in-character rationale. The god has plans for them and will be angered if they get into petty squabbles between themselves. Or at least they have a reason to care about each other.

As for a good seafaring campaign, my main pieces of advice are: 1) read Stormwrack, which has many 3.x rules for such things and 2) decide between you and your players what kinds of things, in addition to running their characters they are interested in doing (like running ship operations, captaining or navigating, etc.) and how detailed they'd like ship-to-ship combat to be. These can be fun additions to the usual character-playing but if players aren't interested it can also be a chore (and one which you can easily take care of by having NPCs take care of those roles).