patricej

be cautious about using a ditch/joining foot that is not part of a walking foot.
that little flange can dig into the quilt sandwich and push/stretch the top fabric so that everything is out of wack by the end of the seam.

an open-to walking foot will give you more visibility as the sandwich moves under the needle.
as you practice you will be better able to get the stitching closer to where you want it.

personally i only attempt stitch in the ditch if i am in the mood to challenge myself beyond reason. lol

otherwise, i either try to echo stitch near the ditch or go with the wavy stitch yolajean mentioned (or some other simple deco stitch that will work with my walking foot.)