Since you did not say in what field you are in I will give my 2 cents from an architects perspective
Use the line tool sparingly
learn the wall tool which has many features
especially inserting symbols and plug-in for doors and windows
which heals the wall automatically
and use the heal tools available to link them together
learn about the loci tool and smart cues to place walls etc..at specified distances
etc......
if you are not designing building
learn to use objects such as rectangle, polygons
think about what the object would be in a 3D world
and use that to draw in 2D