I want to make sure I get the best deals for my textbooks to save some money. Any tips? What are the best places to purchase from? I'm also wondering whether it is necessary or not to purchase the same edition that the university asks for. For example, the Adventures of Huckleberry Finn edition 3 is on my list, but would any edition do?

There are lots of site like locazu.com (mentioned above) which are online marketplaces for textbooks, kijiji is also really good for finding deals. Some schools have student run book stores or small independent stores which have some books.

Editions depend on the prof. Some are adamant that you use a certain editions but others do not mind so long as you ensure the edition does not deviate too far from what is being used. (Also, practice problems will likely be different so if they are assigned you need to use the edition identified by the prof).