Thanks to some words, you can state clearly your agreement or disagreement and you can interrupt people in a polite and non confrontational way.

Use ‘can or could’

‘Paul, can I just ask you…?’, ‘If you could go through them in order…’ Both expressions are more polite than simply saying ‘I want to know…’ or ‘Go through them in order…’

Use ‘would like’

‘I’d like to be’, ‘I would like to be able to show her drawings…’ This sounds much more polite than I want.

Say ‘sorry’

‘I am sorry, but I really strongly disagree…’ This is a common way to soften what you say. You are not really apologizing for what you say. Using ‘sorry’ is telling the listener ‘I’m going to say or do something you might not like, so please don’t get upset.’

Use ‘just’

‘Can I just ask you…?’ The word ‘just’ gives the listener a message that you are not asking them to deal with something difficult or time-consuming; that it is not going to be a problem.

Use ‘I think’ or ‘I feel’ 

‘I do feel quite strongly that we’re bringing this out too soon…’, ‘I don’t think we’ve got any choice…’ These phrases have the effect of softening what you are saying, by presenting your ideas as opinions, not orders or instructions.