I like 2 oz Siete Leguas Blanco (or Tequila Ocho), 1 oz lime, 3/4 Cointreau - I tend to be a minimalist... I want to taste the tequila, and it should be tart. I strongly prefer neutral-spirit based orange liqueurs over brandy based ones.
My preferred recipe
2.0 oz Silver/blanco tequila (OR 1.5 oz tequila and 0.5 oz mezcal for a smokey variant)
1.0 oz Citrus juice, freshly squeezed (1 ounce lime juice OR half ounce each of lime juice and lemon juice)
0.75 oz Triple Sec (Cointreau, Pierre Ferrard Dry Curacao, or Creole Shrub)
0.25 oz Agave syrup (If omitting the agave syrup, bump up the triple sec to a full ounce)
Half salted rim