I believe this style is known as "top shelf, on-the-rocks, no salt". Certainly, I do not like the taste of salt around the rim of a glass.
Fill a cocktail shaker three-quarters full of ice. Add a large measure of the best Tequila you can find and a similar large measure of Cointreau. (I'll leave it up to you to define "large" in this context!)
Squeeze the juice of two limes, one lemon and half an orange (or a whole small orange) and add to the shaker. Shake well, then pour the whole contents of the shaker, including ice, into a large glass. Add a long straw.
If you are drinking this in the hot tub (definitely the best place!), make sure you use a plastic glass.
All that fruit juice - must be good for you!
As an alternative to the orange, you could try using the juice of half a grapefruit (the ruby kind works well), or even two or three small fruits such as tangerines or satsumas.