Rosa:

Welcome to the group. As a new genealogist, I would suggest you begin by getting some software. PAF is put out by LDS for free and is very good software. It is imperative to keep very good records, including sources, from the onset.

Next, I would suggest going to the "Films" section and finding the relevant municipalities to see if they are indexed in the LDS databases. If they are you will see "IGI" or "VRI" buttons next to the film number and description. Clicking on the button will give you the full contents of the film which you can then delimit by surname, first name, etc. Arandas, for example, is fully indexed so if you have the names of your great-grandparents you should be able to find their marriage and/or baptism certificates.

Next, you should find your nearest family history center and order the relevant films where you know or suspect your ancestors information is listed. Indices are often wrong so it is worth verifying and even when they are correct, the actual record has much more information than what is extracted for the index.

You should also browse or search through the user profiles and see if others are researching your towns or surnames. Many of us have found relatives through this group.

It is also useful to download the Nuestros Ranchos user guide which you will find in the "Files" "Reference Materials" section of the site.

Good luck.