Do you mean that the pistils are brown? As in they started out white but have now died back and turned brown. If 2/3+ are in this state, time to harvest.
If in doubt, post a pic and I'll tell you for sure.
For ease of harvest, I usually take the side branches off whole, trim the larger leaves and then hang on a coat hanger by a length of cottton for a week to ten days to dry off. Once dry, I trim the buds offa the stalk.
Basic rule of thumb - touch the buds as little as possible, this way you won't break the trichomes down and oxidise your THC prior to grinding for smoke. Store buds in a hermetically sealed jar to keep them fresh.
In the valley of the norms, the 3 eyed man is king