Be sure to oil it well before using. If it's been sitting for a long time, you really want to oil all moving parts before running it much -- to prevent wear and tear. Use only sewing machine oil -- it's a much finer grade of oil than other types.
Also, check the bobbin area. There's a notch that needs to be positioned correctly under the stitch plate -- I think as part of the bobbin race assembly. (Sorry, it's been such a long time I've forgotten the details. Someone else here will know, tho.)