You've been given some good advice already, I also have graph paper handy so it is very easy for me to check the seam line.
I really suggest you look into getting a "quilting foot". This is used for piecing as we term it, not quilting. It has a 1/4" seam allowance on both sides of the foot (needle in center position) then they also usually have the 1/4" front and back marked. Using that quilting foot allows me to do a lot of nifty stuff when I'm piecing because I can sew with either the seam allowance or the block to the left or right.
I had just started on my Bonnie Hunter Frolic project when my high end machine decided it needed to go to the shop so I did the rest of the project on my very low end Cheapo brother I have as a portable machine and was delighted with the accuracy of the foot!
Here's one use, when you sew triangles sometimes the points get sucked down into your machine. Using the quilting foot alternate the triangles going in and sew on the right/left sides of the foot.