The MBA is clearly a good and very common opportunity to switch careers, so at the very least, you should target a summer internship in b-school in the area you seek. Demonstrating interest by doing something in that industry prior to school would help as well, and would show the summer recruiters how serious you are about a switch. The good news is, you don't have to get a fancy title, I myself worked essentially as a temp with a Wall Street firm before b-school, and that firm ended up hiring me not only as a summer intern, but also as a full time employee when I finished b-school.