For me it depends. If I am brewing a Belgian beer, or anything where I want some complexity from the spices but don't want them to be identifiable I add them near the end of the boil. If I am brewing a pumpkin ale or anything where I want there to be a clean fresh spice contribution I add a spice tea at bottling to taste.
Edit: In making the tea I just steep the ground spices in hot water. No boiling. Then strain with a coffee filter.