Most 5-yar-olds that I know prefer to play than to sit still and study, so your child is not any different! However, children learn all the time; therefore, incorporate learning into every aspect of his day.
First of all, set a good example.
Modeling of healthy behaviors, such as making healthy food choices and physical activity, are crucial to a healthy body. Once your child learns these behaviors, it will be easier to keep these behaviors up later on in life.
Parent also should model other good behaviors, such as not smoking, reading, sharing, respect, not watching too much television etc.
Second of all, teach your child courtesy, responsibility, and encourage high self-esteem.
And last, but not least, stimulate your child with new activities and motivate him to do his work.
Remember that you are the parent; therefore, you are "the boss", and you set up the ground rules of behaviors that you expect your son to do. Make clear to him that braking the rules will mean consequences and let him know what those consequences will be. If he know what is expected of him, it will be easier for him to follow the rules. This rule of healthy discipline work wonders, but you must follow through every time!
Please read articles below for more suggestions.
Suggested readings:
How to teach your child respect
http://pluggedinparents.com/index.php?option=com_content&task=view&id=556&Itemid=204&ed=29
How to teach your child courtesy
http://www.pluggedinparents.com/index.php?option=com_content&task=view&id=225&Itemid=0
How to teach your child responsibility
http://www.pluggedinparents.com/index.php?option=com_content&task=view&id=188&Itemid=0
How to motivate your child
http://pluggedinparents.com/index.php?option=com_content&task=view&id=539&Itemid=204&ed=29
How to encourage your child's high self-esteem
http://www.pluggedinparents.com/index.php?option=com_content&task=view&id=442&Itemid=0
Best regards.