Police Authority Questions

I would like to know when getting pulled over by the police or anyone with the authority to stop ppl on the road, with an officers authority:

-to search you vehicle?
-do you have the right to say no
-and what usually happens after that

-what if your glove department is locked and don't want to open it do you have rights not to open it?

-what if you asked to open your trunk and you don't want to, what are your rights towards that, what is the procedure

What are the procedures of these questions.
Thank you

All of these questions fall under a consideration of probable cause and reasonable suspicion. A vehicle does not have the same expectation of privacy and protection that your house or dwelling does. The police can use virtually anything to establish probable cause. A tail light out, driver inattention, failure to use a turn signal, etc. Once you are stopped, something ELSE can be used to build upon the original reason for stopping.
If you are stopped because you failed to use your turn signal, and the police man approaches the door and he sees you bend down and appear to put something under the seat, he then has probable cause to search the vehicle, based on your actions he witnessed. So, that probable cause (reasonable suspicion you are hiding something by bending down under the seat) is stacked upon the original reason for being stopped. Then, after you exit the car, they DO find something illegal under your seat, they then build upon that probable cause to proceed to search the car. They can ask and you can say no, but that is more of a procedural thing ---you cannot actually PREVENT them from searching the vehicle if they feel they can based on reasonable suspicion or probable cause.

The locked gloved box is an issue, the constitutionality of which has been challenged. While the trunk of the vehicle is considered the same as the body of the car, the glove box, in particular, one that is locked has been ruled to be off limits in rare cases.