I've configured a monog replicaset with the Primary-Secondary-Arbitery architecture but I'm not sure what type of commands shoud the arbiter support. I know that it's purpose is to help elect a new Primary in case of a tie, but I'm not sure what can and should I do on the Arbiter instance, does it require some configuration? or once is part of the replica set I can forget about it ?
Yes, as soon as you have configured it in a replica set you can actually forget about it.
It does not store any data, thus frequent backup is not required. I am not aware of any commands you have to run on it.
Even if the arbiter crashes and your are not able to restart it, then it is easier to delete everything (i.e. the entire dbPath) and connect it from scratch to the replica set. It is quicker than any long lasting trouble shooting.