I have an jpge image which is just a silhouette shape, but I want to trace it and just have an outline of it (no fill). Once I have the outline I might want to tweak it a bit as well, but not absolutely crucial.

I can't work out how to do this in Inkscape. Would really appreciate any help!!

If it's a fairly simple silhouette, Path menu > Trace Bitmap should work wonderfully. Please look it up in Help menu > Manual, for instructions. It will create a path, thereby vectorizing the shape.

Personally, I find Trace Bitmap frustrating to work with. I prefer to import my "bitmap" original and put it in a layer below where I will draw, and reduce the opacity by more than half, and almost 100%. Then I use the Pen tool and trace it by hand.

This (outline, no fill, jpeg) is just what the auto trace in GIMP is excellent at. If you have GIMP I recommend you do it in there and bring the path into inkscape.

trace bitmap is usually the starting point, and a lot of clean up afterwards. instead of mucking about with settings for hours and not getting right results, especially for photos that have a lot of colors and detail you don't care about, much better to create a bottom layer for the jpeg and lock that. then trace by hand on a layer above. i must say that using a computer mouse is next to useless for anything but very minor graphical work. the fairly new range of consumer priced stylus tablets are great.