It seems you can issue your name_firstupdate transaction whenever you're ready (in particular, right after doing the name_new). It won't be included in a block until the name_new is mature (12 confirms) but should be picked up shortly after that happens.
I don't have any source for this other than recent experience, but my names are showing up when I do name_list so I take it that they are properly registered.
EDIT: I thought about it a little, and I suppose you should wait a little bit (at least until your name_new is included in a block). The reason being that nobody can know what name you're trying to register until you do name_firstupdate, and so they can't steal it from you. Sending both the name_new and the name_firstupdate is vulnerable because someone can quickly issue their own name_new for the same name, and depending on luck (or in the worst-case, their control of a significant hashrate) claim it before you can.
Someone more familiar with the intimate details of how requests for the same name are resolved can comment on whether this scenario is possible or not.
Then, how can I know if my name_new has been included in a block? – o0'. – 2012-01-12T10:10:57.833
2 – Sumudu Fernando – 2012-01-12T16:34:21.347
When you do
listtransactionsthere's a field labeledconfirmations; if that is non-zero then it has been included in that many blocks.Alternatively you can check the block explorer at http://explorer.dot-bit.org/; look for your transaction to show up in the list at the bottom.