The direction you point your wireless antenna will affect how good reception you get with your wireless network. If it has multiple antenna point all the same way.
Generally you will have three types of wireless antennas. The first type is the poles, the second is a rectangular type antenna and the third is there they are enclosed in your wireless box (but there are still antennas there).
In the first case with poles you want the antennas pointed straight up or down. They are omni (or all directional) but do not send out the top of the antenna so at the point is a dead spot.
In the second case this is normally a directional antenna and is sending out in the direction the antenna faces and not to the sides or back so point to where you want received.
In the third case they normally have directional antennas enclosed and you should lay the box flat horizontally unless the directions say it can be hung vertically. You can try both ways to see which works better.
Any walls or ceilings between the sending unit and rte receiver will affect the speed and quality of signal received. Microwaves between the two devices will have major effect on the signal as they both broadcast in the same range.