Get lots of lives
If you like playing 1 player, but aren't quite good enough to beat this game alone yet, pick a 2 player game and play all the way to the end of level 1-1, but don't go into 1-2. Beat up all of player 2's lives, then continue as player 2. Keep doing that until all of player 2's continues are gone. Then, you as player 1 must go through the game alone, but if you broke open all the pods during level 1-1, you will have 8 more lives and will have earned more through the points you get beating up player 2. Plus, going through level 1-1 again, you'll get 2 more lives still.