Since "How do I get a BVB ticket?" is one of your most frequently asked questions, this is a try to give you a "How to" about it:
Prices start from 30€ (cheapest seated category), details: http://www.bvb.de/Tickets/Sitzplan
There are a couple of places in Dortmund where you can get BVB tickets, mostly the shops are painted in bright yellow so you can spot them easily. This is a list of adresses we took from the BVB homepage:
The shop marked in left bottom corner is the closest to University. It's right at the "Barop Parkhaus" U-Bahn Station.
There also is an Online-Ticketshop: http://www.bvb.de/Tickets/Ticketshop
And a Callcenter (+49 18o5 3o9ooo). They would charge you 14ct landline or 42ct mobile calls.
As the tickets are always sold out during the Pre-Sales, we strongly recommend to be quick!!! If you are interested in getting tickets, you may ask the sellers face-to-face about the first day of pre-sales!