Watch the setter. The person playing the center position will set the ball high in your direction, arcing it so that it falls close to the net in a position that makes it easy to spike it to the other side. You'll start your approach after the ball is set.
As you practice spiking, make sure you're working with a skilled setter. It should rise and fall in a gentle arc close to the net, putting it in the perfect position for you to go in for the kill.
As you practice with your team, you'll want to call to your teammates to let them know you're striking. Many teams come up with codes for each side, so use them if yours does.