Dun dun dun… One of the more evil topics.
Is tracing ever good? Is it effective? Should I trace?
Maybe, not really, and probably not.
Tracing an image doesn’t do a lot for you. Of course you’ll have the outline, which is always fun, but you won’t gain any experience in drawing, and tracing developes hard lines that are difficult to work with. If your aim is to get photographic perfection in your drawing, it will save you a ton of time to just take a photo of your subject.
Tracing is a good technique for silhouettes, but that’s all I can really do to give tracing any credit. Silhouettes are a comment type of art that can be applied to pencil, pastel, and painted works.
So. What if you just want to have a copy of the outline so that you can practice shading?
I say to draw the outline a couple times to practice accuracy and to learn to keep a steady hand, then you can decide what you want from there. You can trace if you’re using crappy paper; you can use carbon paper if you press very lightly as to prevent hard, non-erasable lines; you could just photocopy your line art and accept that there will be impossible lines to deal with.
Some people claim to learn a lot from tracing; I say that you’ll learn a lot more from actually drawing.