Along with errors and complicated models, the orientation of a print can drastically change the time to print, material used, and surface quality. It is recommended to print on a flat surface and make sure to not have any extreme overhangs.
It is extremely beneficial to have the surface that is touching your build plate be flat. A flat surface allows for strong adhesion to the build plate, easier support removal, and better surface quality. When support is needed on an area that is very close to the build plate, it can be very difficult to remove.
The amount of support material needed can drastically change depending on the orientation of the print. Support material essentially works as scaffolding for any angle more extreme than 45° from the bed. It is normally best to print in the orientation that requires the least amount of support material in order to save time and money. The print quality itself is also much better when oriented in the fashion with the least amount of overhangs.
As mentioned above, it is best to keep extreme angles oriented in a way that will need the least amount of support material. This should be taken into account whenever designing a part for 3D printing. There are numerous 3D designs that look great on the computer but print very rough due to extreme angles and overhangs.