I am using the "create stars & polygons" tool to create an octagon but when I left-click and draw the shape, the angle it starts at seems to be pretty much random I want the base and sides to be "straight" on the screen (i.e. straight from left to right, and straight up and down). However it just seems to always start crooked and you have to manually rotate the shape until it "looks" correct. There must be a way to draw it correct from the start!

In Preferences>Behavior>Steps set the rotation to 22.5 degrees, then hold the Ctrl key down when dragging a new octagon... a little rotate while dragging  will snap to your liking.

I usually hold down Ctrl so that the edges of the octagon are vertical (1) and then rotate 22.5 degrees (2).