A really good margarita will be the most popular drink at any party or bar. Pleases both aficionados and novices. But a lousy margarita will mean you have a fridge full of crappy margarita mix, and people getting sick from shooting the only booze left at the end of your shindig: tequila.
I think it is useful to give proportions rather than measurements in most cases. Perhaps you want to make a batch rather than a single drink. Always build your drinks in a container you can either shake or stir vigorously. Blenders are cool.
4 parts silver tequila
2 parts triple sec
2 parts fresh lime
1 part simple syrup
Shake, serve over ice in a glass with a salted rim
Fresh means freshly squeezed…by you…or a friend…not some juice you buy from the store…get fresh limes and squeeze em…and see how many limes it takes to make a quart of fresh lime juice! And woe to you if you have any paper cuts! Salted rim and ice optional (but ordering it without either is like getting the chicken at a steak house).