To get the salted rim, run a lime wedge around the rim of your glass.
Place the glass upside down in the chili lime sea salt mixture to coat the rim.
Place the fresh jalapeno slices and a few cilantro leaves in the bottom of a cocktail shaker with the lime juice. Muddle the jalapeño slices and cilantro with a muddler to break them up into the lime juice.
Add the tequila and agave nectar to the cocktail shaker with lots of ice. Shake vigorously for at least 20 seconds to mix it all up and make it super cold.
Fill the cocktail glass with ice and pour cocktail shaker mixture into the glass