This is a sticky one for beginners. What you want to do, basically, is to list those positions you had more or less within your field -- ie, you would list a t.a. ship but not a library assistantís job. You should say with whom you were working or working for and what your duties were. This is a good place to list your skills with things that a prospective employer or professor might like to know you had, such as computer skills, experience in lab prep, whatever. As you grow in the field you might divide this up and put the assistantships etc. under employment and create a new subheading of field work.