This means characters that ring true who act and speak in ways we understand (even if we don't agree with them. Maybe especially if we don't agree with them!). It means a strong story with no "weak" points in the plot and to ensure all does ties up (so unlike life!). It means dialogue that reflects how we speak in life but isn't an exact match. There should be no umms and errs etc.
So what is the best way in which you can portray your "people"? Are they coming across on the page the way you mean them to do?