Once you get to know your characters, you'll get an instinctive feeling for how they interact. But to really define those relationships and sharpen the personality of each individual in your story, it might help to tabulate what they have in common with each other and where possible conflict can arise.
I drew up a spreadsheet with the characters' names and types across the top and down the side. I blanked out the irrelevant cells to give something like this:
Here's the filled out sheet:
As you can see, in most cases there are things each pair has in common and things that might cause conflict, if I need to introduce personality conflict into a scene.
Remember that characters don't have to interact for the reader to find out about relationships. Take Characters A (viewpoint character), B and D. Character D works for A and respects her efficiency and authority. But he might describe B to her as someone who shuts himself away, is impossible to get through to, and has no respect for authority. Character A, upon meeting B, won't necessarily see him in the same light because she has more in common with him than D does.
You may never use many of these interactions, of course. In a plot-driven story there isn't the time or the need to go into so much detail. But I find the information handy to have, just in case.