I have a 2 quart slow cooker (crock pot) and I am cooking for two. Do I just half the ingredients called for in a 8 qt. recipe?
As Jay noted above, you'll have to reduce the ingredients by a good deal more than half if your cooker is only 1/4 the size of the original recipe.
The only other thing to note is that depending on what the ingredients are, you may find that the flavor balance is off if you just use math to reduce the amount of every ingredient. Sometimes herbs, spices, sugar and salt don't lend themselves to just mathematical figuring, and you wind up with one thing being too strong or missing from the mix altogether, even when the math is right.
Also, working in smaller amounts, the quality or strength of your ingredients makes a larger difference to the overall recipe. Theres sort of less wiggle room.
Start from using the math (the correct math), but be aware that you might want to tinker with some proportions as you go, or on subsequent batches.