There is Literally Hundreds of Ways to Make a Margarita
The one variable that will never change is the quality of the Tequila that you use. Tequila is made from the Blue Agave plant thats natively grown in Jalisco and certain other areas of Mexico. The leaves of the Blue Agave plant are stripped and the core, also called the Pina, are heated and pressed. Its the juices from this Pina that are distilled into the Tequila you are drinking. Tequilas that are not 100% blue agave are referred to as Mixtos. Mixto Tequila can have up to 49% non agave sugars and sweeteners. Much of the time, these other sweeteners are cheap cane sugars and even worse, chemicals and dyes are added to make it look and taste like 100% blue agave. Hence when you need salt and lime to take these awful liquors down. If you had a bad experience in college, its probably because you were drinking really bad tequila.