The demo of the game is set in stage 2 which is in the Kitchen. The kitchen is a very good stage as it has plenty of traps and surprises.
The bad guys include a sausage throwing fork, beans which jump out at you and plenty more bad guys. The best thing to do against these guys is to avoid them or kill them quickly so they are out of the way. Watch out for hot cooker rings as they damage your health seriously if you jump on them, try to jump around them.
The main weapon in the game is shooting stars or jumping on top of your enemy, these can take time to kill the enemy and they will attack you with weapons of their own. The special weapons take time to implement but are killers when used against any nearby enemy. The best of the special weapons is the whirlwind which allows you to speed across the level killing anything in your path. Another excellent one is the smart weapon which is when you let rabbits jump out of your hat into any enemy near to you. To use these weapons pull back on the joystick until the weapon at the bottom of the screen is highlighted. Then press fire and enjoy.
In the demo you are in the supermarket were you are in charge of a killer tomato. Tommy Gun is armed with a machine gun and grenades so this makes your job a little easier. To fire grenades hit Left Shift.
But the only problem is that they have machine guns and some bad guys hide in the supermarket shelves making it harder for you to shoot them. The only real advice I have is don't waste ammo and kill everything that moves.