First things first. The most important concept for your dog to master is good focus and attention on you, the handler. If your dog is small or a puppy, you may want to start sitting in a chair or on the ground. I use the dogs meals to teach this exercise. If the dog is hungry, this first exercise will be easier for you to teach. Place the food out of reach usually the dog will attempt to get at it, but eventually will give up because it cannot get the food. At some point in this process, the dog will look to you (for help, guidance, or out of frustration - it doesn't matter). As soon as the dog takes a step or looks towards you, press the clicker and immediately give the reward. At this point, they don't necessarily need to be staring into your eyes as long as they are acknowledging you are there. Gradually start to click only when they look at your face. Then vary the length of the look that gets the reward. The length of time needs to be variable, relatively short to begin with (1-3 seconds), then working out to a whole minute occasionally.
To test the dog's understanding of the exercise, hold a piece of food in your hand and show the dog, then hold it away from your body. If they understand the exercise, they know that looking at you releases the food while looking at the food does not. Do this exercise in a quiet place at first, then gradually take it outside the house, to a park, working up to a pet store which should provide plenty of distraction to make sure the dog has a good understanding of what is required.
It is important to remember that dogs are very specific in their understanding of situations, a command for sit in your living room with a biscuit in your hand is different to a command to sit at a busy pet store. This is why we need to take the dog to lots of different places, so that he can learn to generalize his reaction to a command. With this first exercise, build up the distractions slowly, so that the dog can be successful in all situations. This will make it easier to generalize other behaviors later on. Remember to do focus work with the dog beside you as well as in front. This will help with beginning the heel position. Once you are getting consistent eye-contact, you might want to add a command like "look" or "watch me".