When the mission begins, Harry will appear above you and throw a Pumpkin Bomb. Dodge it if you possible or wait until he hovers to one of the end of the screen, then use the time to collect health power-ups if you were hit. If you were not hit, swing towards him and slide the stylus towards him to hit him in the air. After hitting him, swing across him and stop. He will throw the Pumpkin Bomb again, so repeat this process until his health reaches zero.
At the end of the sewer level (Chasing Doctor Connors), use the Web Slam attack on one of the Lizard-men in the pit at the door leading out. It will go through the crack of the door and the icon will be under the floor, where you can't go. The only way to exit is to restart the level.
Make noise to defeat Venom. When you hit him, Sandman will raise his fists off the ground in an attempt to crush you. Dodge this by running through either of his fists. When Harry throws a grenade and it explodes, it will stun Venom for a few seconds and make him vulnerable to all your attacks. Note: You must be nearby when the grenade explodes or else he won't be stunned. Also, there are health packs on the two sides of the building that respawn after you use them. If you are lucky, two may appear in the same location, doubling the health you can receive.
Complete the game and buy all the unlocked upgrades from the store, then exit to the main menu, go to "Options", and go to "Cheats". Turn "Black Suit" on and you will have the black suit on until the game is turned off, making it much easier to find meteor shards.