Charge battery, disconnect battery negative cable. Use a multimeter on the 10 amps scale (dc) connect negative cable of the the multimeter to battery negative terminal and multimeter positive to negative battery cable . Make sure everything is off and that the door are closed. The reading you get should not be greater than 0.050 amps. If greater do like coilster said and remove fuse 1 by 1 until reading is 0 or less than 0,050A. Hood light, trunk light glove compartement and alternator diodes are often the cause.