There are many better ways to draw trees than by drawing lines and triangles in Word. There is a good overview of the main options on this page; below are my suggestions.
This is probably the easiest method once you learn how to use it:
The following programs are meant specifically for this purpose:
You might be able to create decent-looking trees using general-purpose software for creating graphs or diagrams, such as yEd. Having done this a long time ago, I can't say this is my favorite approach…