Note: A fully upgraded Magic Meter and upgraded Zeus' Lightning Blades are required, and this can be done under the Easy difficulty setting. Continue through Chapter 25 "The Furnace" until you find the area where you are stuck between two large bowls dumping flames. Enemies will start to spawn here. Start with the Fires of Ares attack, execute combo, then switch to Zeus' Lightning Blades. Press L1 + R1 until the magic attack ends, then go back to Fires of Ares and execute L1 + Square attacks until you can switch back to Zeus' Lightning Blades again and use the magic attack. Repeat the process to reach a 1000 combo.
When starting Chapter 19 "The Foot Of Apollo", get to the rock Kratos must push. Instead of pushing it, attack that location with the Blades of Zeus and execute the L1 + SQUARE special attack to slowly build your combo to 1,000. Note: This will require a bit of time.
When beginning the game and Kratos fights a single Satyr, use the kick attack against it. Try pushing the Satyr into the corner. Keep it on its back with repeated kicks. Each kick slowly builds your combo, and will take quite some time to reach 1,000.