If the jobs posted aren't exactly what you were hoping for, you can create a job through a self-directed work search. In fact, practicing your job hunting skills may be the most vital employment skill you learn through co-op, as there are many more unadvertised than advertised positions out there. Plus, it's proof that you're the initiative-taking, independently thinking person employers want to see. Once you've decided what area you want to work in, research some of the relevant companies or employers. As with any hiring situation, the more you know the better.
Most companies have web sites.
You can find these in the library. It's useful to have a contact name when you call to set up a meeting. An easy way to ask for an interview is to suggest you meet with the employer to discuss the co-op program. Bring a resume and cover letter with you as well as an information package about the program. Be prepared to discuss the program's benefits for the employer, the wage subsidy process, your own skills, and what sort of position you had in mind or that you think the employer may need.