I use the cut larger polygon method suggested by Darren when I can. It is definitely the most efficient and leads to fewer gap and overlap errors.
Another couple of techniques that I use:
1) use the Trace tool to trace coincident boundaries, then end the trace to digitize the non-coincident boundaries
2) turn vertex snapping on (Editor - Snapping - Snapping Window, click on Edit Sketch and Edit Sketch Vertices). Then, as you are digitizing, hold the V key down which will highlight the vertices making it easier to click on the exact location so that the lines coincide