Cntrmass, what's your general location, Prov/State?
Marten are pretty easy to catch, if they're present. Old growth forests in higher elevations/northern regions that contain red squirrels are a good place to start.
As has been stated, beaver meat is about the best bait there ever was. A little lure that contains beaver castor/oil, skunk essence and or anise is also a good addition to a set. Raspberry jam is another favorite of mine and works as a lure and bait, especially in conjunction with beaver meat. If you can't get a hold of beaver meat, as I see your just beginning, then taint whatever meat you have access to and use that.
Most of my sets are cubbies with a 120 body grip trap, simply because they are fairly resistant to heavy snowfall, which is another condition that usually comes with good marten habitat.
Hope this helps you out.
RO