If we meet with people who always considered himself right, do not try to deny his/her opinion. Do agree in mind until he/she felt his/her truth is recognized and accepted. After that you may try to ask some questions like:
- What if, doing such things be added with ….. (mention your ideas)
- What if, the case of ….. executed first before of ….. (take an example from his/her previous statement)
- If you are really "correct" you can say: "I also think like you before, but eventually I reach the conclusion that ….
You can add other questions appropriate to conditions you have. Pay attention to word what if. It sound more friendly rather than I Think.
After asking the question above you may start to bring your ideas in. Remember any ideas or opinions are come from different backgrounds, different experience, different maturity and different way of think.
Once in a while, there is a possibility that "person who is always right" is in correct, but how he/she talk bring to offend other people in most. Therefore we must remember that we also may be wrong.
My point is do not go in to debate, unless you’re in the debate time. If things had been debated, the pursuing goal of the parties argue only one: How to win in the debate.
Be wise to talk by keeping quiet in the right time.