My local grocery stores do not carry tahini, how can I make it from scratch?
Do you have a local health food/natural food store? If so, they should carry it. If there are ethnic groceries near you, look for Middle East or Indian food; Chinese is a possibility, but the flavor isn't the same as what would be used in hummus, for instance.
Found this: http://suite101.com/article/home-made-tahini-a49997 It looks like you can adjust the oil and sesame seed ratios to your liking.
While making tahini is a really cool thought, you might be better off, financially, just trying to find tahini. If you have any ethnic food stores near you, check them out and don't be afraid to ask. If not, you may want to check online for a reasonably priced tahini.
I found a very reasonably priced tub of tahini in the kosher section of my grocery store.
When outside of the US, I often make my on tahini. I usually make it with untoasted sesame seeds, blended with a small amount of neutral oil. As long as you have a food processor or the equivalent, it's quite simple to make!