I think learning to sew a 1/4 inch seam is in the same category as learning how to drive in the proper lane on the road.
Many of the "modern" machines have a presser foot that "works" instead of buying a special foot - I've found using a piece of graph paper that has the 1/4 inch grids is helpful in "calibrating" where to line up the fabric.
I put the presser foot down so the right edge of the presser foot is right on a line of the graph paper. Then I lower the needle until it punches a hole in the paper - if it hits on the next line to the left, YIPPEE! If not, then I need to adjust either the needle (if it's adjustable) or compensate on how I line the fabric up.
Then after I get things situated, sew consistently - if one has cut consistently, then at least what you're making should turn out to be the same size.