16 tsp (1/3 cup) whole coriander
4 tsp (1 tbsp + 1 tsp) whole cumin
4 tsp whole black peppercorns
2 tsp whole black cumin
2 tsp ground dried ginger
1 tsp whole black cardamom seeds
1 tsp whole cloves
1 tsp ground cinnamon
1 tsp crushed bay leaves

Toast the coriander, cumin, black pepper, black cumin, cardamom, and, uh, cloves? At least all the things that look like seeds. Then grind it all!
You may want to make a half recipe, as this makes 2/3 cup, and it’s the most flavorful right after grinding.

Source: http://indianfood.about.com/od/masalarecipes/r/garammasala.htm