This method is particularly handy for the harder shelled, or older, cannabis seeds, and as you can see them, it?s easy to monitor. Simply place your seeds into a glass of water at room temperature. Allow the cannabis seed to soak for up to 32 hours. Any longer then that, and you run the risk of drowning your seeds before they germinate.
As the seeds begin to hydrate, and swell, some should begin to sink to the bottom of the glass. This is normal, and usually the sinkers are the viable seed, and the floaters are usually not. If your seeds are very fresh, they might even sprout in the glass of water.
After 24-32 hours, remove the seeds, and finish the germination process using the paper towel method, or, just plant straight away into your medium. This method gives the cannabis seeds a bit of a head start, and gives you an indication of their viability.
\You can get the whole story (and other methods of germination) at How to Sprout Marijuana Seeds.