Bitcoin Forum

So I realize this isn't enforced in any way, but is there a standard system by which addresses in a Bitcoin wallet are to be used?

Typically what happens is you request a new receiving address from your wallet.  You receive coins to it.  When you spend coins, the change is sent to a different address (it happens in the background and you don't see it actively happening).  So over time, unless you specifically choose to, addresses aren't reused.

This way if you have 5 people with payments due to you within a short span, you can know exactly who payed what amount versus trying to figure out who payed how much to one wallet.

and in your client you should be able to associate a label with a new address, so you can figure out who paid you.

I reuse addresses only when receiving multiple payments from the same person for the same reason. You should create new addresses for payments from different people or from the same person but for different reasons, because otherwise it just becomes too difficult to keep track of who's paying you for what.