1. architects use different lines for different purposes, but the line type most specific to architecture is drawn with an emphasis at the beginning and at the end. this practice anchors a line to the page and gives a drawing conviction and punch. if your lines trail off at the ends, your drawings will tend to look wimpy and vague. to train yourself to make strong lines, practice making a small blob or kickback at the beginning and end of every stroke.
2. overlap lines slightly where they meet. this will keep corners from looking inappropriately rounded.
3. when sketching, don't "feather and fuzz" your way across the page - that is, don't make a vague-looking line out of many short, overlaping segments. instead, move your pencil from start to end in a controlled, fluid motion. you might find it helpful to draw a light guide line before drawing your final line. don't erase your guidelines when the drawing is complete - they will lend it character and life.
source: 101 things i learned in architecture school by matthew frederick