How to reach Leiden

By Airplane
You can fly to Schiphol (Amsterdam) airport and catch a train from there, the trainride will take about 20 minutes and costs €5,30.
The other closest airport is Rotterdam Airport. From the central station it takes about 30 minutes to get to Leiden and it costs €6,60.
Another option is to fly to Eindhoven Airport, you can catch a train from there on. This trainride takes about 2 hours and costs €18,80 (Ryanair only hits Eindhoven so this actually is a really good option)

some websites you might find usefull:
www.ryanair.com

www.skyscanner.net

By Train
If you're not coming from too far away or you're flying to Germany or Belgium, you might consider catching a train.

International trains can be found on these websites
http://www.nshispeed.nl/en (dutch international railways)
www.bahn.de (german railways)
http://www.belrail.be/E/index.php (belgian railways)

and the national railways can be found here: http://www.ns.nl/cs/Satellite/travellers

By bus
http://www.eurolines.nl/?lang=ENG You can catch a bus to The Hague or Amsterdam and catch a train from there on to Leiden Central Station


Other important things to have in mind...
The participants will be sleeping in a gym so they need to bring a sleepingbag and something to sleep on.
In November chances are that it will rain alot so they also need to bring an umbrella.
It will also be cold so they need to bring warm clothes! (temperatures around 5-10 Cº)