As the title says I am currently in the middle of creating my first custom adventure. It is a multi-part adventure with branching missions and choice missions that will end in an assassination mission on an Imperial politician. Any tips/advice for a first time creator?

NEVER Listen to the Order 66 Podcast!

Episode 7 is The List for encounter design. Given that adventures are comprised in large part of encounters, this is a handy dandy reference to have.

Plus, download The List in pdf format.

Episode 22 is GMing A-Z with Jay Little. The creator of the game goes into detail about he preps for his own games, and I have found his advice incredibly useful. In my spare time, sometimes I just make alphabetical lists of possible adventure hooks and plot elements.

Episode 45 is The NPC Deli, where they give you all sorts of great advice for creating NPCs.

Honorable mentions...one of which will probably help you get where you want to be...

Episode 35 is about designing a Convention Module, which is an adventure with very specific parameters, so that can be fun.

Episode 56 is a long one, but worth a listen, as they get into high-level campaign construction

Episode 21, Isn't It Episodic, talks about how to write Episodic adventures, which is sort of in-between Con Mods and Story-Arc Campaigns.

NEVER Listen to the Order 66 Podcast!

Episode 7 is The List for encounter design. Given that adventures are comprised in large part of encounters, this is a handy dandy reference to have.

Plus, download The List in pdf format.

Episode 22 is GMing A-Z with Jay Little. The creator of the game goes into detail about he preps for his own games, and I have found his advice incredibly useful. In my spare time, sometimes I just make alphabetical lists of possible adventure hooks and plot elements.

Episode 45 is The NPC Deli, where they give you all sorts of great advice for creating NPCs.

Honorable mentions...one of which will probably help you get where you want to be...

Episode 35 is about designing a Convention Module, which is an adventure with very specific parameters, so that can be fun.

Episode 56 is a long one, but worth a listen, as they get into high-level campaign construction

Episode 21, Isn't It Episodic, talks about how to write Episodic adventures, which is sort of in-between Con Mods and Story-Arc Campaigns.

Thanks, i'll not give them a listen later

If part of the campaign is about clue-gathering, this is critical:

http://thealexandrian.net/wordpress/1118/roleplaying-games/three-clue-rule

I'm a big fan of AngryDM, encounter structure advice here:

http://angrydm.com/2013/05/four-things-youve-never-heard-of-that-make-encounters-not-suck/

And other articles here:

http://www.madadventurers.com/category/journals/angry-rants/

One thing I've found liberating is to not be too married to an end result. Pushing things in a direction is one thing, but sometimes events and the players have different ideas. For my current campaign, all I've done is set things in motion. Key NPCs have motives and direction, but the players can interrupt/hasten/avoid/ensure those directions as the campaign progresses. Sometimes an NPC dies and I need to insert a successor, who might push things in a different direction.

Don't give the players a railroad (Point A has clue to Point B. Point B has clue to Point C.) The players will find a way off of it without you trying. Give them obvious A or B (or even C) options. Once they choose, it does not mean you have to throw away the unused option, you can pull it back in later.

Sometimes the old ways are good ways. One of the things I have found I like to do when looking at structure on a new campaign is to use note cards, thumb tacks, yarn and a bulletin board I can push them into. I'll put objectives on the cards, especially the first few and the last ones. Then think of other options and put them on cards. Then link them with the yarn and see how many connections I can either connect or places where I should disconnect them. As long as you don't live with another player you can leave this up (not a good option for me) and make changes or modify it. The ability to have a perspective on the whole thing at one time is very very useful. Once I have it firmed up pretty well, I'll take a photograph or two of the whole ball of wax (just in case I need to rebuild it) and then I'll either build it in my wiki and link them together as best I can or type it into my notes if i am not using my laptop so I can still go back and forth.

The temptation is to put a lot of detail into the entirety. Understand the entirety of your story arc and have an outline that leads from place to place and list out any key NPCs they are going to encounter. You also want to have a few details for each of the places you visit. It sounds like a lot, but not really. It is more of an overview so if you go off on a tangent, you know where to go back to. Do your detail for the coming session without fleshing the whole campaign out. Then after the session, you will know where to go with your next bit of detail. If you write detail and description for everything first, you'll be heartbroken by the end of the third or fourth session. You'll also be tempted to force the players down the railroad instead of letting them choose their path. They will get to your story elements but you may find them going down Route 66 instead of Interstate 20. If California is your destination, they will eventually get there. Let them help build the story as you go. In time you will get better at pacing and knowing what you need to write down to kick off each session.

Have a list of names ready to go for NPCs with a brief description (hair color or height, scar or crooked nose) and an attitude or saying. The players will surprise you. Keep things rolling as best as possible. If you need an adversary and have a deck to go with the name and description, even better (but not necessary).

Breathe. Remember, this is about fun. It's easy to get wrapped up in details and worry. Let it go and focus on having fun and the story will flow more naturally. Soon you'll be looking forward to how they are going to be responding to what you are throwing at them or scratching your head figuring out how you are going to stay one step ahead. And realize you are smiling because it is fun!

I agree with Gray 100% about not railroading. Don't try and lock the players into a singular course of action without a pretty good reason.

That said, also be sure the players always have a direction to go, and they know what it is. There's a difference between a sandbox campaign that can take nearly any seemingly random encounter and tie it into the main plot and quest chain, and a "sandbox" that just has the players wandering around aimlessly and getting into trouble while the real story happens in a far off land away from them. After all is said and done, everything should always point the players to the next objective, whatever that may be.

Also roll with the punches. If the players go in an unexpected direction, try and make it work. If things get too out of hand, just call it a night early and take it back to the drawing board. You can usually take anything the players do and turn it back onto the plan with a little effort.

Don't be afraid to pull punches either. Just because a Z-95 can carry missiles, doesn't mean these Z-95s the players are about to fight are currently carrying missiles. Most combat encounters are designed for the players to win. It's just a matter of how hard they have to work for it. Even the encounters the players are supposed to lose should usually have an escape hatch, even if the players aren't smart enough to use it.

And going beyond your Wound Threshold (if you’re in personal combat) or above your Hull Threshold (if you’re in space combat) doesn’t automatically mean you’re completely dead/destroyed.

If you’re over the threshold, that just means you’re out of the fight.

Now, for minions, for cinematic/story purposes, it may be easier to just say they’re dead if they’re over their threshold.

But Rivals and Nemesis NPCs and player characters should be made of tougher stuff, and they may be down, but they’re not necessarily dead.

One thing I've found liberating is to not be too married to an end result.

QFE. Every scene (encounter), whether it's procedural or dramatic in nature, should pose an immediate question which is then answered by the struggle during the scene. Once the question is answered, the scene is over. So be prepared to have the encounter go both ways.

I'll recommend Hamlet's Hit Points by the great Robin D. Laws.

Some GM resource Websites

http://thompsonpeters.com/eote/misc/NPCgen/ = NPC Generator

https://triumphdespair.wordpress.com/ (the EotE alphabet is great = https://triumphdespair.wordpress.com/edge-of-the-empire-alphabet/)

http://www.reddit.com/r/swrpg/wiki/despaird100 = Things to do with Despairs

http://bastionkainssweote.blogspot.com/p/shipyard.html = Ship stat sheets