Before you are allowed to enter Puerto Vallarta, you must fill out a white and green sheet of paper that is your customs declaration. You will turn this in after you have picked up your luggage and give it to the customs personnel. Passengers may bring the following new or used items that make up their personal luggage as a part of their duty-free exemption:

(Sorry this list is long and sometimes oddly specific, the entire list is on the form itself so be sure to read through it all and make sure you are in compliance...here are the highlights!)

Items for personal use (i.e. clothing, including bridal items, footwear, beauty items)
Baby items such as portable cribs, strollers, etc.
One laptop, ten DVDs, thirty CDs, one video game console and five video games
Four fishing rods, three surf boards, one camping tent, one pair on binoculars
Two musical instruments and their accessories
A hand toolset with its storage case, which may include a drill, pliers, sockets, screwdrivers, etc.
Medicines for your own personal use (must be able to show a prescription for psychotropic substances)

Passengers older than 18 years of age can import a maximum of 10 packs of cigarettes, 25 cigars, or 200 grams of tobacco.
Passengers older than 18 years of age can import up to three liters of alcoholic beverages and six liters of wine.

Senior Citizens and people with special needs can import items such as walkers, wheel chairs, crutches, canes, etc.

Up to three pets (pets meaning cats, dogs, canaries, hamsters, ferrets, turtles, etc.) as well as accessories needed for their transport and cleaning provided the Zoosanitary certificate issue by the Sagarpa is provided to personnel. 

Passengers may import goods of duty, additional to personal baggage, as long as they prove their value with a receipt does not exceed $500 USD when coming by air.