Pour a little sweetened lime juice onto a small plate. Then pour some salt on another small plate. Take an empty glass and dip it into lime juice. Gently shake off excess, then dip into salt. Again, gently shake off any excess. Fill the glass with ice.
For drink:
Combine tequila, Grand Marnier, sweetened lime juice, and grapefruit juice in a separate container. Shake well.
Pour over ice, squeeze and garnish with lime and grapefruit wedges.