guidelines are:

1) There must be a mission description, a backstory if you will. Who made the mission and why. 

2) There must be requirements to join the mission. How many people maximum? Any rank requirements? Do people have to have a certain number of Pokemon or a certain type of Pokemon? That sort of thing. 

3) What are some goals that will have to be completed in order for the mission to be successful?

4) What rewards are you going to offer? Each person must receive the same reward. The rewards you offer and the number of people participating will effect how many CP your mission will cost. 

4a) CP cost Formula: 
(TP reward for each participant) + (TP value of any items awarded to each participant) = (Total TP value awarded per person) 

((Total TP value awarded per person) / 10) x (0.5 x (the number of participants)) = Total CP cost (rounded up to the next whole number)