First, welcome to the forum.
Second, as long as nothing has been disturbed you only need two things, fuel and spark. Spark is easy to check by taking off a spark plug cap, shoving a screwdriver into it (ignition OFF and wear gloves!) and hold the shank of the screwdriver 1/8"-1/4" away from something metal like the engine. Get an assistant to turn over the engine a few cranks and look for a spark between the screwdriver and engine.
Fuel is a bit more complex, a) yes do you actually have fuel as Ozziedog suggested, but b) is it getting into the carb? You can disconnect the fuel pipe from the carb and put the end into a clean jar/bottle, and get the aforementioned assistant to turn over the engine a few times. Fuel should squirt out into the jar if the fuel pump is not knackered. If it IS coming out, and you have spark, it may be that the fuel is not getting into the carbs jets (blocked float valve perhaps?). If NOT, take the pipe off the other side of the pump and see if any fuel comes out of it. If not, it could be a blocked fuel filter.
Also, you may not know, but there is an automatic choke on most carbureted buses. Before starting you press the accelerator all the way down and release it, and if the engine is cold that engages a stepped lever on the throttle which chokes the carb. As it warms up it releases it. Pretty cool when it works.
Incidentally there are several workshop manuals/books which have detailed "It wont start - what do I do?" sections. Certainly the Autodata manual has a good one, maybe the Haynes and Bentley manuals do (I can't remember), but I definitely recommend the book "How to Keep your Volkswagen Alive" by John Muir is written from a very different perspective but I think it's quite good for people just getting started with mechanical stuff and aircooled VWs. If you don't mind the 60's hippie (hippy?) tone, then its quite entertaining too.
Good luck.
