So any one got tips for being a DM, my friends they are pretty chaotic and I am probably not going to be able to stick to the book.

I have said it multiple times before. DMing is a bunch of improv.

You don't know what the PCs will do, that's why it's better to walk in with a gist of what will happen rather than a fully thought out campaign.

Hope this sort of helps

The fact that you already know your players and by the sounds of things you were one in the same group is an advantage. You already know what types of hijinks and shenanigans they are likely to get up to. 

Being a player in our group before taking over as DM it definitely having some semblance of understanding as to how they think.  

Try doing a dungeon adventure and starting them in medias res, that can cut down on the randumbness. Then give them some randumb things in that dungeon, like a big red button that says DO NOT PUSH and summons a LOT of angry mephits or a magic doorway that turns everyone into gnomes for 10 minutes. That way, they can express their crazy in the field, and you can justifiably ask them to tone it down in town. Or better yet, you can just ask for a quick recap of their actions every time they go into town and run a series of crazy delves.

Also, the strongest tool in your box is the phrase “are you sure you want to do that?”

Quote from Daryll_Goodfellow_King_Of_Random >>

I have said it multiple times before. DMing is a bunch of improv.

You don't know what the PCs will do, that's why it's better to walk in with a gist of what will happen rather than a fully thought out campaign.

Hope this sort of helps

 Ditto this. Have some encounters, scenarios, and conversations outlined out -- then let the players interact with the world.

You can have a 100% plan for how the session is going to happen -- but all that is going to change when a player decides to punch a guard in the face. A 50% solution with a lot of room for improv is going to be a more fun experience for both you and the players.

Quote from Daryll_Goodfellow_King_Of_Random >>

I have said it multiple times before. DMing is a bunch of improv.

You don't know what the PCs will do, that's why it's better to walk in with a gist of what will happen rather than a fully thought out campaign.

Hope this sort of helps

I have just DMed my first adventure. It was also my, and all but one of our group's, first ever D&D adventure. This was the best advice anyone could have given me (picked up from Youtube videos)! My players actually stuck pretty well to the "script" (which surprised me), but having a very loose outline allowed things to progress naturally and stopped me worrying about whether they would derail my carefully laid plans.

All in all, it was a success. It did take a lot longer than I expected (I thought it would take 1-2 hours tops, but lasted over 4 hours...), but all my players loved it, as did I. We are now all completely hooked :)

You don't know what the PCs will do, that's why it's better to walk in with a gist of what will happen rather than a fully thought out campaign.

Although I agree with this to some degree...

... the reality is that I'm pretty awful at "pantsing" it (i.e., flying by the seat of my pants). I suck at making up maps on the fly, verbalizing descriptions of things out loud on the fly, etc. I am awesome at that when writing it out ahead of time. But bad in the moment. I'm great at deciding how monsters or NPCs will react to PCs... great at doing battle tactics (once the map is there), and that kind of thing. But if I tried to run a session just with a vague idea of what will happen it would be... ugly.

And I do not have time to make up every area of the world, every town, every NPC ahead of time just in case the players want to go there (no one does). So either the players have to be wiling to accept a little gentle prodding about where to go ("this NPC friend of yours went into this forest and is missing" or "the mayor offered you 200 gp to clear out the haunted crypt"), they're going to have to accept very long delays between sessions as I try to prep whatever unexpected place they decided they wanted to explore. Or if they don't like that, they need another DM.

The reason I say this is as follows: When you are DMing, it's very important to discover, by paying very careful attention, your own limits. Know what you are good at, and what you are not. Play to your strengths, and try to avoid, whenever possible, your weaknesses. If you're like me and good at writing, but not good at orally improvising, place or NPC descriptions, then knowing that, write them out ahead of time. If you're bad at coming up with good maps on the fly, draw them out ahead of time, and so forth. As a new DM, you won't know your strengths and weaknesses before you start, but it won't take long at all to start figuring them out. So the most important thing is pay attention... especially to your players. People-watch them, as it were. They will tell you through actions, body language, and exclamations during a session what they liked and didn't like. That will tell you what your strengths and weaknesses are.

One thing to remember- the PCs can't see the big picture.  That means that even if they do something random you can still just shift the plot over in their direction so they trip over it.

I know it's not ideal, but if you're running a written module and the characters are going completely off the rails, it's okay to just say, "Hey guys, the plot doesn't expect you to go that direction, so if you decide to go that way everything's going to slow to a crawl while I improv something and look stuff up." Don't tell them they can't do that, but it's okay to break immersion every once in a while.

Quote from TransmorpherDDS >>

I know it's not ideal, but if you're running a written module and the characters are going completely off the rails, it's okay to just say, "Hey guys, the plot doesn't expect you to go that direction, so if you decide to go that way everything's going to slow to a crawl while I improv something and look stuff up." Don't tell them they can't do that, but it's okay to break immersion every once in a while.

Great advice.

Also you could say, "Well since the book doesn't have this, we need to stop for tonight and you'll need to give me a couple of weeks to prep something before we can play again."

Quote from BioWizard >>

You don't know what the PCs will do, that's why it's better to walk in with a gist of what will happen rather than a fully thought out campaign.

Although I agree with this to some degree...

... the reality is that I'm pretty awful at "pantsing" it (i.e., flying by the seat of my pants). I suck at making up maps on the fly, verbalizing descriptions of things out loud on the fly, etc. I am awesome at that when writing it out ahead of time. But bad in the moment. I'm great at deciding how monsters or NPCs will react to PCs... great at doing battle tactics (once the map is there), and that kind of thing. But if I tried to run a session just with a vague idea of what will happen it would be... ugly.

And I do not have time to make up every area of the world, every town, every NPC ahead of time just in case the players want to go there (no one does). So either the players have to be wiling to accept a little gentle prodding about where to go ("this NPC friend of yours went into this forest and is missing" or "the mayor offered you 200 gp to clear out the haunted crypt"), they're going to have to accept very long delays between sessions as I try to prep whatever unexpected place they decided they wanted to explore. Or if they don't like that, they need another DM.

The reason I say this is as follows: When you are DMing, it's very important to discover, by paying very careful attention, your own limits. Know what you are good at, and what you are not. Play to your strengths, and try to avoid, whenever possible, your weaknesses. If you're like me and good at writing, but not good at orally improvising, place or NPC descriptions, then knowing that, write them out ahead of time. If you're bad at coming up with good maps on the fly, draw them out ahead of time, and so forth. As a new DM, you won't know your strengths and weaknesses before you start, but it won't take long at all to start figuring them out. So the most important thing is pay attention... especially to your players. People-watch them, as it were. They will tell you through actions, body language, and exclamations during a session what they liked and didn't like. That will tell you what your strengths and weaknesses are.

I think I may have overstated.

I had several encounters, locations, NPCs etc planned out. However, I didn't plan exactly where things should occur, or exactly how interactions would go with the NPCs. I made them "modular" so they could happen if, when and how they were needed.

Woah... I gave good advice?