It depends on how the campaign was conceptualised. Is it a straight-up go from A to B and kick evil in the face, or something else?
As far as interaction with NPCs, I'll usually let dialogue go until information needs to be extracted, where the dice rolling comes in play. I tend to reward good role-playing with information or bonuses on rolls. I generally keep the dice rolling to a minimum, and let the players inquire about making rolls (roll Persuade to be let inside the club, roll Insight to see if bouncer is bullshitting you, etc).
Just don't chase the players around all game long from plot point to plot point, unless that's what they want.
