I have a '94 that lives outside in upstate NY. A couple of places to look:
The body of the vehicle, where the round weatherstrip on the door contacts, was fairly rough - with the horizontal run over the door speaker area, water would sit there and leak in rather than run forward. I put a closed cell, dense foam weatherstrip piece on where the door weatherstrip would hit it. It creates a better seal and squished the round weatherstrip on the door harder.
The odd shaped rubber piece on the door; it's at the intersection of the forward edge of the window, the round weatherstrip on the door, and just ahead of the door handle. I had removed it once (it uses double sticky tape to stay on) to replace speakers. Make sure it's glued on well.
Here's the hard one to find: The forward facing end of the roof seal. Not the seal facing down, but facing forward. Tightening the latch keys harder doesn't compress it more.
Last, the side rails of the roof frame - are they straight? If they seem bowed in, you may want to straighten them Biff of V-Mania has the details, but basically you can heat them in an oven and bend them straight.
Let me know if I can add detail or help more...