Semi-experienced 3.5 DM running Pathfinder for first time

[incarnate236]

After having played and run several 3.5 games over the past few years I'm going to be taking my first stab as a GM for Pathfinder and was wondering if anyone would share some of the big rule changes a GM should know? I understand the classes and races are different in some minor aspects and that the skill tree is much more condensed but what changes greatly affect roleplaying and combat mechanics?

[JusticeZero]

Combat maneuvers are different. Some skill mechanics have changed beyond just condensing them. Some class features work differently. Spiked chains don't have reach. Some feats and spells work a little differently. There are a lot of subtle changes, but not much that's big.