I've only done this once and am not that familiar with DTW, but I'll give it a shot. From the UA gates you will follow the signs toward baggage claim (past security and down the escalator). You will then go out to the curb and pick-up the inter-terminal bus and they will eventually get you to the parking garage adjacent to the Westin. From there you will follow the signs to the Westin (basically up an escalator into the NW check-in area. The signs are pretty good and easy to follow. As an aside, allow at least 30 minutes from UA terminal to hotel and vice-versa. The airport buses seem few and far between and there is a considerable distance between terminals. As far as I know you cannot walk from the UA terminal to the Westin even if you want to since the NW terminal is in the middle of the airport. The Westin is a nice hotel and treats Starwood elites pretty well; however, the hotel is much better if you are flying NW versus UA. Hope that helps!!!