Info on playing SSBM online:
If you plan on playing SSBM online, you should follow some basic rules so you have the best, non-desynced gaming experience.
1) Space button presses apart by at least 1 second outside of an actual battle (like in menus), more depending on your connection.
2) In those same menus, if you move your control stick, after you stop moving your control stick, stop for at least a second before making a button press.
3) Just in case there is any desyncing issues, before starting a battle, from the character select screen, go into the rules screen (click at the top of the screen) and back out. All characters should be properly chosen now, even if they weren't before.
4) Let player 1 do all of the menu navigating. If any other player butts in, there can be some major menu desyncing.

 

Player 1:
42451170 03AA0000 // x prev coord high
42451170 03AB0000 // x prev coord low
42451170 03AC0000 // y prev coord high
42451170 03AD0000 // y prev coord low
42451170 00A60000 // Ground Velocity High
42451170 00A70000 // Ground Velocity Low
42451170 00700000 // Air Horizontal Velocity High
42451170 00710000 // Air Horizontal Velocity Low
42451170 00720000 // Air Vertical Velocity High
42451170 00730000 // Air Vertical Velocity Low
40451170 00089F00 // Platform ID
40451170 00008C00 // Facing Direction
42451170 0C480000 // Real Damage High
42451170 0C490000 // Real Damage Low

Player 2:
42452000 03AA0000 // x prev coord high
42452000 03AB0000 // x prev coord low
42452000 03AC0000 // y prev coord high
42452000 03AD0000 // y prev coord low
42452000 00A60000 // Ground Velocity High
42452000 00A70000 // Ground Velocity Low
42452000 00700000 // Air Horizontal Velocity High
42452000 00710000 // Air Horizontal Velocity Low
42452000 00720000 // Air Vertical Velocity High
42452000 00730000 // Air Vertical Velocity Low
40452000 00089F00 // Platform ID
40452000 00008C00 // Facing Direction
42452000 0C480000 // Real Damage High
42452000 0C490000 // Real Damage Low

Player 3:
42452E90 03AA0000 // x prev coord high
42452E90 03AB0000 // x prev coord low
42452E90 03AC0000 // y prev coord high
42452E90 03AD0000 // y prev coord low
42452E90 00A60000 // Ground Velocity High
42452E90 00A70000 // Ground Velocity Low
42452E90 00700000 // Air Horizontal Velocity High
42452E90 00710000 // Air Horizontal Velocity Low
42452E90 00720000 // Air Vertical Velocity High
42452E90 00730000 // Air Vertical Velocity Low
40452E90 00089F00 // Platform ID
40452E90 00008C00 // Facing Direction
42452E90 0C480000 // Real Damage High
42452E90 0C490000 // Real Damage Low

Player 4:
42453D20 03AA0000 // x prev coord high
42453D20 03AB0000 // x prev coord low
42453D20 03AC0000 // y prev coord high
42453D20 03AD0000 // y prev coord low
42453D20 00A60000 // Ground Velocity High
42453D20 00A70000 // Ground Velocity Low
42453D20 00700000 // Air Horizontal Velocity High
42453D20 00710000 // Air Horizontal Velocity Low
42453D20 00720000 // Air Vertical Velocity High
42453D20 00730000 // Air Vertical Velocity Low
40453D20 00089F00 // Platform ID
40453D20 00008C00 // Facing Direction
42453D20 0C480000 // Real Damage High
42453D20 0C490000 // Real Damage Low