Wii Sports was full of tips and tricks, but these are the only ones we have been able to rustle up for Wii play:

Alternate Laser Hockey Paddles
If you press A and B together before the game timer starts in Laser Hockey you will switch to an alternate paddle.

Medals Section:
This is how to unlock Platinum medals.
This content is under fire, as several users have reported different scores to get a Platinum, so until we get the real data compiled, we will leave it up in the air.

Thanks to Peej:

During the one player shooting range if the b or a button is pressed on the second controller another cursor will pop up and when that second player shoots it will count towards the one player score. The most I got was 623.

Thanks to sean:

Platinum in tanks is 30 missions with 125 kills, after you beat 20 missions with 84 kills then play again.

If you have any more, feel free to send em in, or comment here!