Come, Sit and Stay
Let your dog know what you want from them by first establishing yourself as pack leader. Patience and modest but firm force may be needed to obtain the appropriate behavior. This can be challenging when you are training your dog to come when called.
Dogs are exploratory animals and will turn things over and dig and scratch. When you are having a training session you need to minimize distractions as far as possible. This may mean being away from the voices of others in a clear area with just a few small objects on the ground.
Use a dog's spontaneous behavior when they approach you by executing a command/hand gesture that is unique to the behavior you require and may not necessarily use outside of training.
If you want the dog to come then start by facing your dog and getting it to sit, then back away and command the dog to stay. Next use the chosen command and hand gesture and praise lavishly when the dog behaves correctly.
Repeat the sit and stay, stepping further back, put the dog back in the sit/stay position if it comes too soon and try again. If the dog doesn't come then use a treat or favorite toy to encourage it.
For dogs who are slow or reluctant learners using the collar and leash in training can be useful. Put the dog in the sit/stay then back off, slackening the leash as you go, if the dog refuses to come then give the lead a gentle tug while at the same time issuing the command and the hand gesture.
Use a long lead and wrap it around a port or tree if your dog comes too readily. If he gets up early then gently tug the leash and use the stay command if there is not a tree or a post then find a partner to help you. However, this can make the dog confused about who it should obey; keeping its focus on one person is more efficient.
Patience and persistence are needed with all training; dogs don't immediately understand the usefulness of human induced behavior such as come. Don't speak harshly as this is counter productive, establish your status as leader with a firm voice and correct body posture while you wait for the dog to comply.
Most dogs are eager to please their owner and respond to being praised when they behave appropriately.