One help is to select boards that are closer to a rift or quarter sawn
cut. Look at the end of the boards and you want to see the rings
running as nearly straight across the thickness of the board as
possible.

Couldn't agree more. Also, you didn't say, but did you use some kind
of mechanical alignment device such as dowels or biscuits? I have
found these to be most valuable in pine, less valuable in harder,
denser woods.

I also cheat with pine on table tops and put a couple of slats of 1X2
on the bottom and glue and screw through the 1X2 with a screw that
stops 1/8 from coming through the top.

While I am thinking of the bottom, don't forget to seal it when you
seal your top. A wood that is movement prone like pine will move even
more dramatically if the moisture is allowed to leave on only one side.

One last thing, if the ends of the boards are moving, your only hope is
a breadboard type trim. You rarely see any type of pine furniture
(never soft pine) without an edge treatment.

I like pine, and have made some antique reproductions out of it and
they turned out quite nice. I have used it at client request for pine
cabinets, etc. It is good stuff if you like the look and you want to
(or are getting paid to) work with it.

Robert