First prepare your glasses, rub the glasses in lime juice and then cover the rim in salt and a bit of chilli flakes if you like some spice. Place in the fridge keep cold until ready to use.
In a shaker combine the tequila, Cointreau, and lime juice. Fill with ice and shake for about 20 seconds.
Fill your glass with ice and strain the margarita between 2 glasses. Garnish with lime or a slice of jalapeño for some spice.