If you want to toast your sesame seeds (recommended), preheat your oven to 300 degrees
Place at least 1 cup of sesame seeds (the more the easier it is to blend) onto a cookie sheet that has sides
Roast your seeds for ~5 minutes, or until toasted. Keep a close eye on them. You want them to be golden brown
Once roasted, pour the seeds into a blender (alternatively you can use a food processor)
Blend, but stop to scrap down the sides ~every 45 seconds
Be patient, when you think it is done, I recommend blending for one more cycle to get it really melty
Once finished, scrap out into an airtight container (I store mine in the fridge)
Use it with any dish that calls for tahini!
The more sesame seeds you use, the easier it is to blend
I highly recommend toasting your seeds. It enhances the flavor quite a bit and helps the seeds to release their oils more easily when blended.
In general, once you start smelling the seeds, they are done, but keep a close eye on them!