When you are pulled over for a standard traffic stop, the police offer is not allowed to search your vehicle, unless you give them reason to.
If you are pulled over, keep in mind that the cops are shining their lights into your car. They can see your movements even if they are still in their cop car, so do not try and shove things under seats or throw things into the back seat. If you do this, the officer will likely see, thus giving them suspicion and even the right to search your car. In fact, you should not even reach for your license and registration until the officer asks for it. Rummaging around in your purse and glove box without the officer fully knowing can be alarming for them.
If you simply pull over to the side of the road as instructed, remain calm, and keep your hands on the wheel where they can be seen, you will be fine. Roll your window down as instructed and only get your documents when asked. If all goes well, and the officer does not have reasonable suspicion that you are dangerous or involved in crime, then he or she cannot search the rest of your vehicle, without a warrant. However, keep in mind that anything that is in plain view is at risk.