Find a company that reimburses for tuition. These companies are typically larger, and can be found online in yearly reviews (CNN Money, Fortune Magazine and the like), as well as listed on blogs and group websites (fatwallet.com).
Convince your employer that particular classes or degrees will apply directly to your current role. It's important that what you want reimbursed for be applicable to your position, and not completely out of the realm of your work.
Find partnerships between your current or potential employer and colleges or universities. This will make it easier, as reciprocity could exist between work and school.
Commit to terms that your employer could offer you. These terms might include a period of employment following completion of a course or degree program, as well as academic standards that need to be upheld.