Boxes in heavy forest cover aren't as critical as boxes in open habitats. There are a few nest box placement options that should be avoided. First, the entrance hole should not face a busy street or highway. The adults flying to and from the box risk being hit by a fast moving car. Second, the box should not be in a major human use area.
Adult birds are reluctant to select a box in an area with lots of disturbance.
If the box is selected, the adults may not have adequate opportunity to make enough feeding trips to the box to maintain healthy young. If in an urban setting, the box should be near escape cover so when the young fledge they can hide and not be eaten by a house cat before developing strong flight capabilities. Another consideration for a successful nest box experience is the likelihood of predation. Some nests are always destroyed by predators, so complete protection is probably not practical. However some precautions are often warranted.