FROM PFT website pft1881.org

YOUR WEINGARTEN RIGHTS
(from Union Summer School Education & Training Department)
Weingarten Rights - Right to Union Representation in An Investigatory Meeting That May Lead to Discipline
You have the right to union representation during an investigatory interview with the employer if you believe that the interview may lead to disciplinary action. An investigatory interview occurs when a supervisor questions you to obtain information that could be used as a basis for discipline. 
The Basics
1. You must ask for union representation! You must be proactive and request that a steward or union site representative be called into the meeting. 
2. You must have a reasonable belief that discipline will result. 
3. You have the right to know the subject of the meeting. Ask the supervisor what will be discussed at the meeting. 
4. You have the right to consult with your union representative. You have a right to meet with your steward or union site representative before the meeting. And, you are entitled to pause during the meeting and to step outside to seek the advice of your union representative. Your union representative may also speak during the meeting.
5. You do not have the right to a union representative of your choice.  Representation may be based on the availability of a steward, site representative, or other union representative.
6. If your Weingarten Rights are violated - don't refuse to attend, but repeat your request for a steward. You shouldn't refuse to attend the meeting, if the employer denies your request for union representation. But, you should repeat your request for representation, take good notes, and don't answer any questions. Immediately report this situation to your union representative following the meeting. 
7. Weingarten is only for investigatory meetings. Weingarten Rights don't apply if the employer is simply informing you of some discipline which has already been decided. They only apply if you are being questioned. 
History:
The U.S. Supreme Court established this workers' right in the private sector in 1975 (NLRB v Weingarten 420 U.S. 251). This right was also made applicable to employees covered by the California Educational Employment Relations Act (Redwoods CCD v PERB 1984)
Learn more: Know Your Rights! A guide to workplace laws for classified employees and paraprofessionals in California​