Step 1
For a salted rim: Spread the salt on a small plate, a little bigger than your glass. Run a slice of lime around the edge of the glass and then dip the glass into the salt, rotating as needed to cover the edges of the glass. Fill the glass with ice.
Step 2
Add ice to a cocktail shaker (or a jar with a lid if you don't have a cocktail shaker). Add the tequila, lime juice, orange juice, and agave. Shake for 20-30 seconds. Strain into your glass with ice. Top it sparkling water if desired. I like to use lime, lemon, or grapefruit flavored seltzer.