DM Advice:

1) Breath and keep calm... No matter what happens the players will look to you the DM as the person to steer them in the right direction.

2) If using an AP.. follow the script but don't forget your players if they do something that is off the wall. Embrace it. Don't worry about embellishing scenes in the AP. If a player has a really cool idea don't dismiss it because its not on the written page but rather write it into the AP. The most important thing is to have fun.

3) Make sure you read the rules and have the rule books at hand. They understand its your first game and most good gamers and friends will understand if you need to look something up once in awhile to get the answer. I would know as much as you can but sometimes smaller rules pop up.

4) Rules grey areas. Each and every system including pathfinder have grey areas where things are not spelled out fully. Your the DM you can make a ruling that is thematic and the way you see it. Just explain to them this is how you are going to handle this and your will be good to go.

5) If the AP story is a little dry and you find your players dosing off or losing interest. Spice it up. Add in some Roleplaying oppurtunities or a NPC that isn't in the AP. Maybe a wandering begger or merchant. Just make sure the experience is memorable.

6) Character Death: This is tough and usually not an issue in an AP game but can happen. Sometimes dice hate players or the players do something so out of the box it backfires. This can be tough. But don't white wash it. Tell a story. make the last moments of the character memorable. Paint a cinematic picture of the death. Give it time to sink in. Maybe hold a memorial service or name an NPC building after the character. After the emotions of that moment die down. take the actual players out for a drink or milkshake and hang out as friends. In the end we are all friends playing a game for fun. :)

7) Challenging combats. The combats in an AP are usually balanced if not usually in the players favor. Just watch the CR's and ECL. more then a 1 or 2 level difference in either direction can lead to a bad combat. The monster involved also can be made more challenging with envirmoments. Using what is around will make a more immersive game.

8) Try and make sure each player has a chance to shine. a big mistake new DM's make is they have one PC that is more interesting to them and so they focus the story on that one persons character. this can lead to feelings from the others of being left out. Setting up moments in every games where one member of the party can really shine is great. Even if not intentional. If a player roles a huge crit out of nowhere you can really play that up and build that player's interest in your game.

9) Watch the level of loot given. Again in an AP not usually an issue because the treasure is predefined. But there is nothing that will end a game quicker or make people unhappy when a DM gives an overpowered item to a player without realizing it and they cant get it back. you have a couple of options either in story make everyone else match that power level or in some way remove the item in a fair way. Usually exchanging it for a lesser one to balance. this can be done by having an NPC show up looking for the item and offering a trade. Or come up with some other reason. A story reason for removing the item from the equation that also furthers the charecters experience and gets them other loot is far better then saying woops I messed up lol:)

10: Finally and this is the most important advice ever: you are friends and there to have fun. Don't let things get out of hand where that can become an issue. Sometimes emotions get high. Its the DM who needs to see this and if you need to end a game early to let people cool off or calm down. don't hesitate. there is nothing in a RP game that is worth losing a friends over.