JOEL - You should always honor and follow the policies of the work place and school. There are a couple of main legal limitations regarding discussing of religion at work or school:

1. An employee must not allow religious discussions to interfere with work. This should mean that there is nothing wrong with discussing religion with your co-workers during your break time or lunch time.
Student religious expression in school may be limited if it substantially interferes with or disrupts the school's activities or if it involves active proselytizing.

2. If a co-worker indicates directly or indirectly that he does not wish to discuss matters of religion, you should immediately stop discussing it with him. If you don't he is justified in filing a complaint of harrassment.

How strictly these are followed depends a lot on the employer and company or school policies, and whether the institution is private or public. Perhaps you can get a copy of your work's or school's policy regarding the discussion of religion and determine from that just how far you can go without getting into trouble. A no tolerance at all policy at both work and school seems a little extreme.
The best thing to do is be a good example of Christlike living so that your actions may prompt those you know at work or school to ask you about your beliefs outside of the school or work setting.