If you're stopped by police

You have the right to remain silent. If you wish to remain silent, tell the officer.
Stay calm. Don't run. Don't argue, resist, or obstruct the police. Keep your hands where police can see them.
Ask if you're free to leave. If yes, calmly and silently walk away.
You do not have to consent to a search of yourself or your belongings.

If You're Stopped In Your Car

Stop the car in a safe place as quickly as possible. Turn off the car, turn on the internal light, open the window part-way, and place your hands on the wheel.
Upon request, show police your driver's license, registration, and proof of insurance.
If an officer asks to search your car, you can refuse. But if police believe your car contains evidence of a crime, they can search without your consent.
Both driver and passengers have the right to remain silent. If you're a passenger, you can ask if you're free to leave. If yes, silently leave.

You do not have to let them in unless they have a warrant.
Ask them to show you the warrant. Officers can only search the areas and for the items listed on the warrant. An arrest warrant allows police to enter the home of the person listed on the warrant if they believe the person is inside.
Even if officers have a warrant, you may remain silent. If you choose to speak, step outside and close the door.

Do not resist arrest.
Say you wish to remain silent and ask for a lawyer. If you can't afford a lawyer, you have a right to free representation.
Don't say anything, sign anything, or make any decisions without a lawyer.
You have the right to make a local phone call. The police cannot listen if you call a lawyer.

As soon are you able, write down the officers' badges and patrol car numbers, which agency the officers were from, and any other details you remember.
Get contact information for witnesses.
If you're injured, seek medical attention immediately and take photographs of your injuries.
File a written complaint with the agency's internal affairs division and civilian complaint board.

All information above is from the SC ACLU