Start With The Outside First: Start with the gutters, typically made of aluminum they are light weight and easy to take down. Get up on the roof, rip off any metal, (sometimes copper) flashing from the roof. This can be found around the edges and corners of the roof. is there a storm hatch? Those heavy pieces of copper can be worth a lot. They will be a pain to remove but worth it.
Hit The Garage: If the house has a garage, it can be a gold mine. Depending on what the garage doors are made of you could have a mini gold mine on your hands. Don't forget to check out the insides of the garage as well. Old appliances can be found in here, which could have bountiful amounts of copper or other materials to scrap.
Inside The House: First and foremost, you'll want to develop a plan to scrap all the copper pipes and wires. This is going to produce a lot of sheet rock and other debris. For this entire project, you'll have to rent a dumpster. Appliances will also be a source of scrap metal. Baseboards will also provide great weight in scrap. Look around for any furniture that might have metal legs.
All in all, getting an opportunity to scrap a whole house is a great money making experience. Depending on how much time you have to complete the project, you may want to consider hiring a labor hand. Remember to take your time and separate your metals. Secure your work site as well, you don't want scrap thieves to come and take all your handwork.