This might seem like common sense, but a lot of students, and hobbiests trying to turn professional, seem to send off their tapes blindly to companies they have heard of, without any thought about the job descriptions and requirements of the company. Landfills full of VHS tapes, and thousands of hours of company time scanning through reels, are wasted because of this. There are a lot of different positions. Some require a certain amount of production experience, others are entry level. Others will train you in their software after you are hired, and hire based on artistic qualifications as a character animator, texture map painter, etc.
Some positions are very specialized, especially at larger studios and for feature film work.
One person or department might spend years just building 3D models, which would then be textured, lit, animated, and rendered in different departments. Others jobs are more general, especially at smaller companies and game developers, where one artist might be given his own shot to animate from scratch, or her own environment to design and render. Knowing a range of skills, from modelling to compositing, would be a big plus at these companies. The organization Women In Animation has a useful web site with profiles of people's careers. Some positions require that employees sign a long-term contract, binding them to work for the company for a specified number of years.