Do yourself a favor and get some videos from Elknut.com These will not be hutning videos with a little advice thrown in like most that you see. What he tells you is what elk are saying and what to say back. Best money you will ever spend.
As far as extra equipement for the bow itself. I have never needed them, but always carry a spare set of cables and bowstring, just in case.
I carry 3 calls, because you never know what will turn up a bull. The absolute best if you can master it is the diaphragm mouth call. Basically a glorified turkey diaphragm. If you have ever called turkeys with one, it should be easy. Otherwise there is a definate learning curve, but there is no other call that can make the variety of calls you need to sound "real". My second call is a Primos hyperlip single. It is a blow call, and takes a bit to master, but is a good one. I also have a hoocie mamma as a backup, but don't use it near as often as the other two.