This is the step that will help accuracy. Once you've found the incentre point, draw a perpendicular line (using the 90 degree edge of your set square) from one side of the triangle to the incentre point. This line is now the radius if your incircle so set your compass to the length of this line, then swing that baby around
Just make sure your pencil tip is as blunt as possible, therefore you can't but get the circle to touch all three sides!
Im did tech graph for JC and was pretty good at it, and they were pretty harsh on docking marks for inaccuracies like those.
So I found a few ways to make all these constructions pretty god dam perfect
Firstly, when you're bisecting an angle or line, set the length of your compas really long (as in go way outside the triangle). Anyone doing physics, back me up on this one, reduce percentage error FTW!
Also, sharpen your pencil like crazy for constructions, then snap the top off with you're fingernail so as when you draw the circle, its wider and more likely to touch everywhere you want it to
Last point, if you wanna go hardcore, get a real compass, as in this:
They really help and especially since were allowed plot and measure our co-ordinate geometry questions, being able to measure distances accurately is going to be very important