Be patient to the process. Sometimes things will move slowly, or the paperwork will seem cumbersome, but remember the tremendous numbers of people, and goods, that cross the border every day and there needs to be a system in place to track it all.
Mexico requires that any non-Mexicans that are traveling in country to conduct business must have a business visa called an FMM (Forma Migratoria Multiple).
Things always run smoother when the paperwork is done right. Make sure you have your passport, or your Global Entry card, when you cross the border and don’t forget to get an FMM before you visit a business in Mexico.
Talk to your customs broker and freight forwarder and make sure they have the right documents from you and the right number of copies they will need to make sure your shipment isn’t the one to get a red light from customs OMCC -- Customs Brokers, Freight Forwarders & Trucking.
Before you go across the border, check with your cell phone provider to understand what international programs they have that you might be able to take advantage of and don’t be afraid to just turn your phone off for the day if you’re not going to be gone for an extended period of time.
If you are planning on using your credit cards for restaurants or hotels, contact your bank ahead of time you can put an international travel voucher on your card that will only allow your cards to be used in Mexico for the times that you will be gone.
If you decide to convert your USD to Pesos to have cash on hand for taxis, etc., there are plenty of shops available for you to do this as soon as you cross the border. Other than for taxis and parking or tips, it’s not mandatory to get Pesos if you are only going to be in Mexico for a short visit.
If you are going to be flying to cities in Mexico other than the border towns, you might want to look at using the Cross Border Xpress which allows you to park on the US side for only $15 per day and walk across an enclosed bridge right into the Tijuana Airport Terminal. From this airport, you can grab a flight to virtually any city in Mexico.
If you’ve parked your car on the US side in one of the many secure parking lots and you are walking back across the border, don’t forget to bring your US passport, or your Global Entry card, with you as the lines for people with these documents are considerably shorter than for people that don’t have these documents. OMCC - Public Parking
Crazy as it sounds, less than 5% of Americans have a passport but, if you think you might be traveling to Mexico on a somewhat regular basis, it’s worth your time to get one. You can file an application for a passport at your local post office and within a few months you will be all set.
The shortest of all lines coming back across the border are for those people with a Global Entry card. This is a card that is issued through the US Customs and Border Protection CBP - Global Entry through their Trusted Travelers program and gives you access to special processing lines when you are coming back into the US.