During a visit you have a chance to discuss your research interests. It's also your best opportunity to highlight your skills and show your enthusiasm for attending that particular graduate school. If you are able to communicate these qualities to faculty, your odds of receiving financial support increase. Your work experience is likely to be discussed. If you worked with a professor on a research project, knowledgeable discussion of that project will demonstrate an understanding of the research process.
Many financial aid offers require service as a teaching assistant.
Any experience in this field should be emphasized. Often departments participate in research centers that indicate research specializations. This information is available in numerous resources including Peterson's Guide to Graduate Programs in Engineering and Applied Science, ASEE Directory of Graduate Engineering and Research Statistics and individual departmental web sites. Clearly, it's advantageous to apply to universities where your research interests coincide with departmental strengths. Because you may not be able to choose the exact project you want to work on, faculty will look positively on a degree of flexibility on your part.