Employers differ in their requirements for you to qualify for tuition reimbursement. You may have to be an employee for a designated period of time before you can become eligible. Your course grade may also determine if you get reimbursed for a course. Some employers will reimburse you for courses where you've earned a 'C' or better, for instance. In any case, ask your employee benefits department about the tuition assistance opportunities.
Many employers have a cafeteria plan that includes tuition assistance.
Other types of tuition assistance your company may offer include scholarships, grants and loans that are available for employees or their children. See IRS Pub.