1. Whatever the issue - bring it up in private. When you bring up disagreements in public those not involved feel out-of-place and uncomfortable. Also, their opinion of you is lowered.
2. Be sure of what you want to say, do it as soon as you can and deal only with the facts. Know what you want to say before bringing up the issue and don't let a lot of time go by before you say anything. Letting the issue sit will not make it go away but will make it bigger. Resentment sets in when there is a problem or a difficult situation and nothing is being done to solve it.
3. There may be many issues that you want to discuss but discuss only one at a time. Too many issues at one time can be overwhelming and it will be difficult to come to a solution.
4. Keep your voice at a moderate tone and do not speak in an accusatory manner. Using a loud voice and an accusatory tone can be intimidating and will be seen as aggression and can lead to a battle of words where no one listens and both parties lose. For those more timid, when faced with an intimidating person they will retreat, say nothing or say anything to keep the peace.
5. Give the person a chance to state their feelings or opinion and if you think you have heard something that you do not like, ask them to repeat it and try to understand - do not get defensive. Sometimes when we assume we know the whole story and in our quest to be 'right' we only half listen. Instead of listening to understand we listen to contradict. Listen to understand
6. Look at the issue from their point-of-view. Do not assume you know what the other person is thinking or that you know the whole story. Do not bring up things that the person cannot change.
7. Treat the person with respect and try to come to a solution that will benefit both parties. If you were wrong apologize.