What would a planet wide Blockade look like? I read in the "Strongholds of Resistance" book that one included 4 Star destroyers, but what about the support craft and Tie Fighters? I am building up my Edge of the Empire crew to make a smugglers run past a blockade and I am wonder what I should put in their path.
We've been playing for a while so they can take the heat.
Well in that Star Wars Rebels episode they only had 3 imperial ships blockading that world and they needed a serious escort to get past them!
The real questions I think need answering are;
1) How many ships are trying to punch through the blockade at the same time?
2) Will your players take the time to investigate exactly how the Empire are blockading their destination?
3) Even if they get through they still need to get back out after they make their delivery so will they have backup?
I'd suggest asking them to discuss how they're going to pull this off perhaps emphasize the danger by COMPNOR releasing a video of the latest failed attempt making it very clear this is much more dangerous than Star Wars Rebels ever revealed!
Ideally they need multiple diversions ala the Firefly pilot episode as well as a couple of decoys to draw off most of the blockades fighters and maybe an imperial ship so they can catch them unprepared but that still requires them to make their delivery and worst still collect whatever they've come for and escape the world in a way they can reach hyperspace before any of the Star destroyers get within range especially the interdictor!
They could use a stolen imperial code and get down to the world without the imps suspecting ala ROTJ but are any of them force sensitive and is there anyone able to detect them aboard the imp ships?
Actually if played carefully they could get in and out without problem, but how would you like it to turn out?
It depends on how hard you want to make it and what kind of resources the players have. For instance if all they have is their freighter to sneak by then two to three TIE squads and support vessels may be over kill for the group. Also another factor is how important the world being blockaded is. The bigger the importance to the Empire the more ships that will be involved in the blockade.
Should heavily depend on the planet they're blockading and why. Possibly more important, are they breaking in or out? And do they need a return trip?
A ship has to come out of hyperspace a long distance from a planet's gravity well and takes some time to approach it, giving a blockading ship time to detect and intercept them. If their ship is fast, they may be able to outrun the blockade, if not avert detection. An Imperial blockade may place ships in the paths of known hyperspace lanes. If your players plot a diversion through hyperspace to arrive in an unexpected quadrant, they may have a better chance of running the blockade.
I've found in my game that the concept of gravity wells and hyperspace travel is very important to define. How far does a ship have to be from a planet before it can escape to hyperspace? How easily can it travel outside of known hyperspace lanes to make such a diversion? I assume that astrogation maps need to be updated regularly to account for movement of stellar phenomena, so if you don't have an up-to-date chart for space that's off the beaten track, you'll have to do some complex calculations to account for the change. It's not like you can just look at the constellations because you're seeing light that's many years old.
At least that's the explanation. It seems like space is mostly empty so why shouldn't you just be able to point the ship in a random direction and Punch It? Because it's not as interesting narratively if you can get away too easily.
In the Tarkin novel they talk a lot about how plotting hyperspace usually uses hyperspace beacons within each system to mark the established routes, so a blockade could be oriented towards the hyperspace beacon because they know the vast majority of ships are going to appear there.
This could be why smugglers can charge 20,000 credits just to fly someone a couple systems over - because they know a route that takes them not to the beacon so they can hopefully avoid detection.
It depends what the blackade is supposed to stop.
A single wing of TIE's in the right place will be able to drive off any civillian ships trying to run the blockade but won't stop a heavily armed freighter or a proper warship.
Any kind of Star Destroyer in the right palce will be able to stop anything short of a full military attack.
So the way to run a blockade is to either punch through the defenses using force and speed or do it via cunning and stealth.
The way I see hyperspace lanes is the navigation data for these lanes is easy to get (cheap to buy to full public domain. Most systems will want you to be able to visit them so might just give the data away) and are guaranteed safe because they are used alot. This may only be one way in/out of a system or two ways in/out for a system on a lane. Outside of these standard lanes the information is very valuable as it may contain shortcuts on shipping routes etc. So to blockade a planet you may only need to put a ship on these specific points as this is where 99+% of all traffic will come. For people running the blockade they will need to have nav data to be able to come out of hyperspace from a point that will not be covered and then fly in fast or come out of hyperspace a long way away and stealth in.
You really need to know the goal of the blockade as well. Are they blockading a major world, with many starports, and heavy traffic? A major fleet would be required to stop that many ships. Is it a minor rim world that they really only care about a single city? Then they may have heavy coverage over the city, and only sensors or recons ships for the remainder of the planet. Also, are the ships designed to keep people in, out or both? A lot of thing to consider if you plan a whole blockade. Also is it fully established, or are they still setting up? A hasty blockade is much easier to break.
Solo blasted his way out of Mos Eisley against multiple star destroyers that were looking to keep people on the planet. They had recently arrived, and weren't a very tight net, and it was concentrated on Mos Eisley. They probably weren't concerned with people arriving, other than to warn them that if they land, they won't be allowed to take of again.
Contrast that with the Trade Federation blockade of Naboo. Fully established, many ships. Designed to stop traffic both ways. But a fast, well defended ship could fly by, and escape if it could avoid destruction for a few rounds.
A key point is whether the ones doing the blockade are in control of the surface, and if they are not, is the surface offering any resistance. A blockade against a hostile armed world is very hard, unless you're willing to bombard it...
think the iron blockade from uprising.
A ship has to come out of hyperspace a long distance from a planet's gravity well and takes some time to approach it, giving a blockading ship time to detect and intercept them.
Not anymore. 
Anyway, there are two possible actions here. Firstly, the escaping ship needs to evade any covering capital ships and fighter. But, more importantly, the blockaders will need to have fast ships stationed around the planet to chase any ships that do manage to get into hyperspace. Which is why I've been meaning to write-up some hyperspace chase rules for EotE for awhile now.
In Ep4, the Empire was pretty certain that the MF contained the droids so they used their Star Destroyers to give chase. They might not be that willing to do so if unsure who the escapees actually were. So one option is to use a fast ship to act as a decoy (ala Mad Max Road Warrior) to distract there pursuers.
As to getting in. The real trick would be landing without getting blasted into dust. There's an episode of the Clone Wars, where a squadron of CR-90s go through a blockage to drop off supplies to trapped Clone troopers. That might be some good inspiration. I think it's Season 3 episode 3. Another one to watch is Season 1 episode 19.
There's been a few episodes of Rebels season two showing Imperial blockades and how to blitz through them. It seems that while Star Destroyers make the backbone and lynchpin of their blockades Arquittens-class light cruisers do much of the heavy lifting and dealing with smaller, less suspicious ships. As they're not statted up yet the Vigil-class Corvette would make a suitable fit.