In this C++ tutorial for Unreal Engine 4 I'll explain a few ways to log information to the output log and the game viewport.
AddOnScreenDebugMessage (Also known as Print String in Blueprint)
UE_LOG macro to log messages in categories with different severities like log, warning, error, verbose.
DrawDebugString, drawing string at 3D location in the world.
More info & dev updates: http://tomlooman.com
Twitter: / t_looman