Rules of Earth's original Dragonballs: 

• Must gather all seven Dragon Balls.
  
• A chant is needed to call out the eternal dragon.
 
• One wish can be granted once the eternal dragon (Shen Lon) has been summoned.
 
• After the wish is made, the dragon will disappear, the Dragon Balls will turn to stone and scatter themselves around the Earth the balls will remain stone for one year.
 
• The eternal dragon can't grant wishes that are beyond the powers of the creator of the Dragon Balls.
 
• A person can be brought back to life or any group of people that fit into a specific category, only if they didn't die of natural causes.
 
• If a person has been brought back to life before, the person cannot be revived again.
  

Rules of Earth's new Dragonballs:

When Kami-sama merged back with Piccolo, the Dragonballs turned to stone. To bring the balls back Dende, from Namek, became Earth's new Kami-sama. Dende was able to change the rules of the new Dragonballs around. Some remain the same while others are different.

• You must gather all seven Dragonballs.
  
• A chant to call out the dragon is still required.
  
• This time three wishes are allowed instead of one.
  
• After the wishes are made the Dragonballs will turn to stone and scatter around the world, they will remain stone for one year.
  
• If only one wish is made, the balls will turn to stone and stay stone for 4 months.
  
• The dragon can't grant wishes that are beyond the power of the creator.
  
• A person can be brought back to life or any group of people to fit into a specific category, only if they didn't die of natural causes.
  
• If a person has been brought back to life before, the person cannot be revived again.
  

Rules of Namek's original Dragonballs:

• Must gather all seven Dragonballs.
  
• A chant must be made in Namekian language calling out the eternal dragon (Porunga)
  
• Wish has to be said in the Namekian language.
  
• Three wishes are allowed.
  
• After the wishes have been made, the dragon will disappear, the Dragonballs will turn to stone and scatter around the world, they will remain stone for 130 days.
  
• The dragon can't grant wishes that are beyond the power of the creator.
  
• Anyone can be brought back multiple times, as long as they didn't die of natural causes.
  
• Only one person can be revived back per wish.
  

Rules of Namek's new Dragonballs:

When the Nameks settled on their new Namek, the new Guru changed some of the rules made by the old Guru.

• Must still gather all seven Dragonballs.
  
• Chant to call out the eternal dragon must be made in Namekian language.
  
• Wish to be said in Namekian language.
  
• Three wishes are allowed.
  
• After the wishes have been made, the dragon will disappear, the Dragonballs will turn to stone and scatter around the world, they will remain stone for 130 days.
  
• The dragon can't grant wishes that are beyond the power of the creator.
  
• A person can be brought back to life or any group of people who fit into a specific category, as long as they didn't die of natural causes. Note: This is basically the only change the new Guru made.