Know the facts. It will save you time in the long run. As soon as someone else questions your accuracy, things are going to slow down. You will be sent back to do your homework and your thoroughness will be in question.
Don’t assume. As far as is possible go right to the source and get your information. Then take the time to review that information well before presenting it.
Effective people are respected because they have good information at their fingertips. If they don’t have it, they are given grace because they know where to find it fast. Those who are perceived as guessing and assuming don’t garner many points on credibility and reliability.