In multiplayer, there are many stages and rules to organize. If you're playing on a normal field, I recommeend Hyperbombs. Thy blast through anything, and it's easy to trap people (Unless they have bomb kick/punch). What you do is lure them to a back corner and lay a bomb by every opening so it's likee this:
O=Bomb
[ ]=Brick
Y=Enemy
...O...O...O...O...O
[ ]..[ ].[ ]..[ ].[ ]..[ ]
............................O
[ ]..[ ].[ ]..[ ].[ ]..[ ]
.........Y.................O
----------------------------
As you can see, no matter where they go, they are pretty much screwed.
In Lotsa Items, go for remote control. Get the good items only
UNLESS it's your FIRST items OR you havee nothing good already. I recommend Line Bomb and NO BOMB KICK and Bomb Kick makes it hard to walk near bombs without sending them flying away. Have a peace treaty and practice chain reactions. BE SURE TO LEAVE A 100% SAFE SPOT FOR YOURSELF!!! So when they come in and lay a bomb, press B. Depending on how wide your chain reaction is, you can blast them into oblivion. It's pretty intimidating when you know how to use remote bombs. They won't even wanna go near the tunnels connecting the screens! If they set foot inside, go to your safe spot and BOO-BOO-B-BO-BOO-BOOM!!!