If you want to add an optional garnish, start by cutting a lemon or lime into slices. Pick one slice and cut a small notch in the middle of the pulp. Place the slice on the rim of your glass using the notch to hold it in place.
Fill your glass with ice. You want enough ice that the glass is almost full.
Use your jigger to measure out 2 oz of whiskey. Add your whiskey to your glass with the ice.
Use your jigger to measure out 4 oz of 7up. Add your 7up to your glass with the whiskey and ice.
Use your bar spoon to get everything mixed together. Make sure not to stir too hard or the soda will fizz.