Use Teamwork
Do Not Block
Establish the Three Ws (Who,What,Where)
Use Suggestions to their Fullest
Physicalize

The Story Event
The Style Event
The Character Event
The Theme Event
The Life Event

Do not Block
There are not many rules in improv. However, there is one rule you should be bound by honour never to break: do not block. Blocking is contradicting a teammate's offer. For example, if your teammate approaches you and says: "Hey mom, what's for dinner?" Don't reply, "I'm not your mother!" This is blocking. While initially funny, blocking rapidly loses its appeal, shatters your scene's illusion, and breaches the trust your teammates are placing in you. 

Establish the Three W's (Who, What, and Where)
An improv scene must basically show the Who, the What, and the Where. 

Who
In an improv scene, you have four minutes. Use those four minutes to develop your character, through dialogue and actions, so that the audience learns to care for or despise that character, whichever is most suitable. Remember, seeing a well- developed character interact sincerely with other characters within a situation is funnier than a bunch of out-of-context one-liners. 

What
The What is the main action of a scene. It is usually not difficult to establish, since you either have a scene structure or are given a scenario to begin with. The tricks to the What are incorporating the use of audience suggestions into your scenes, and finding unusual choices in presenting and concluding your scenes. 

Where
The Where is often the most difficult W to convey. You must show the audience where you are by creating an environment, and interacting with that environment, throughout your scene. To do this, you must physicalize. 

Use Suggestions to Their Fullest
Most improv scenes require suggestions from the audience. Suggestions are the variables in an improv scene, assuring that each scene is fresh and completely new. When you ask for suggestions from the audience, don't just use them once in your scene and then forget about them. Find as many ways as possible to incorporate your suggestions into each scene. 

Physicalize
There are two types of physicalization, both of which are equally important for developing the Where of a scene. The first type of physicalization, also called miming, is accomplished by creating items out of thin air. If you ever need a mop or a guitar on stage and you don't have one, just pretend you do. The audience will believe you. The second type of physicalization, is accomplished by using teammates as items. If you ever need a chair or a car on stage and you don't have one, get your teammates to transform themselves into one and use them. 
 

 Example Scene: You are late for your wedding and you must explain to your fuming bride- or husband-to-be why you are late. Act out the story as you tell it, with the help of your team.

The Style Event 
In the style event, a team selects a style, such as horror, drama, documentary, etc. The team must then accurately present all aspects of the given theme within the allotted four minutes. 

 Example Scene: You are presenting a scene in the style of a nature show. The suggestion you request from the audience is "a job". The audience gives you "computer programmer". You must present a scene about computer programmers as though it were a nature show. You might pretend to film computer programmers in their natural environment. You might talk about their eating habits and mating calls. Etc.

The Character Event
In the character event, a team must perform a scene in which they develop characters and their pertinent characteristics through dialogue and action. 

 Example Scene: You are presenting a scene that takes place at a bus stop. You ask for two characteristics from the audience. The audience gives you "annoying" and "heartbroken". You present a scene about an annoying tourist and a heartbroken truck driver interacting as they wait for the bus. 

The Theme Event
In the theme event, a team is given a theme, prepared by the organizers, which the team must explore as thoroughly as possible in four minutes. This is most often played as a series of short skits, called a harold, in which each skit shows a different interpretation of the given theme. 

 Example Scene: If your theme was "love", you might begin with a skit about an elderly couple falling in love, followed by a skit about a young couple's first kiss, followed by a skit about a tennis match where the score is 30-love, followed by etc.

The Life Event
In the life event, a team must present a scene from a teenager's life, prepared by the organizers, attempting to make the scene as natural and sincere as possible. 

 Example Scene: You have been in an accident with your parents' new car. You must confront your parents over the situation.