Nothing special is required. Be aware that they now use the red light green light system. Get the green light you go, get the red light you might have the vehicle searched but they don't tear it apart like Canada does. Someone might stick their head in the door and that's it.
Do watch the yellow lines when crossing the border. Stay behind the line until the vehicle ahead of you has cleared the lights and wait for them to signal you forward.
If you have pets, they might ask you for the papers. Have a copy of them just in case they want a copy, it will save you time.
Take your sunglasses off just like going into Canada so they can see the whites of your eyes.
Do not speed going through Sonayta and come to a complete stop at the stop signs. They do have radar and use it to their advantage
Coming back to the US is a different story. You need a passport and then depending on which lane is open, you might have to so some serious maneuvering. Again sunglasses off. The wife and I stop talking as soon as we get near the last building on the Mexico side.
