I use the #1 foot and follow the edge which is 1/4" away. Make sure you sew on the top so that you can see where you're sewing. I also like to do this with my bobbin thread, so it doesn't show.
Here are some examples of topstitching. Most topstitching done is on garments that also have edgestitching (go here to learn about edgestitching). They can go together without looking out of place. The most common place that topstiching is found is on men's shirts. This is a shirt I made my husband.this one I made.