Our own nest boxes are not huge successes but the one that does get well used faces NE and is well away from the feeders (and rival birds). You may have to compromise but you want the box to be out of direct sunlight ,so that it does not overheat, and not face prevailing winds and the rain they bring. The boxes also need to be out well before the breeding season as they are scouted very early on. We didn't realise this with our first ones - we were taking them down in winter to avoid rot and putting them back up too late.