People do things that we don't like. Sometimes habitually. We complain to them in order to convince them to change their behavior. A complaint cannot force a change of behavior, however, it can only be an influencing factor. A complaint can influence in two ways: it can provide new information to the listener and it can have an emotional impact on the listener. We want our complaints to carry the maximum amount of influencing power so that we have the best chance of obtaining the behavior that we desire. 

People don't like to change. Change is sometimes difficult and sometimes scary. People also don't like to be judged negatively by others. There are powerful incentives for people not to listen to our complaints. But people also like to be judged positively by others, especially those whom they respect and trust. If we can ask for what we want in a way that spares others from the pain of being negatively judged and that preserves their respect and trust in us then we have the best possible chance of getting what we want.

'''Therefore:'''

Use factual requests to ask for changes in behavior. Avoid making negative statements about others. Criticize ideas and techniques; don't criticize the ''people'' proposing them.

When making negative statements about behavior use factual, accurate, and precise information. Avoid making global negative statements that include or imply words like "always" and "never". The smaller the negative statement is the more likely it is to be heard. The more accurate it is the more likely it is to bring about a change in behavior that is desirable. 

Take responsibility for your emotions and your opinions by using "I" statements: "When _____ happens I think/feel _____". Avoid using "you" statements: "You _____ me" or "You made me feel _____". These are negative judgements that will be engender resentment and do not contain data that will help the listener to choose new behavior.

When asking for change ask for measurable changes in behavior. Another persons behavior is the only thing that we can actually know about them. Their attitudes and emotions are buried deep in their brains beyond our direct access. Use examples when it is impossible to describe the behavior in specific terms. 

Finally ask for as few changes as possible in a single episode. Focused requests are more likely to receive a positive response.

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Did I mention that it's much easier to talk about than it is to do? It turns out that effective communication often does not provide the relief that can be gained through an uncontrolled outburst. -- PhilGoodwin

Yeah. It's not the least bit cathartic. It's just more effective.

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See also ConstructConvincingArguments, StopComplaining