I brought Barney home yesterday (10 week old cockatiel), and I've started target training a little already. He was out this morning and a little bundle of energy, so I stuck him on his T stand and we had a bit of a go. Went really, really well (he was following the stick around the perch), but I suspect he was more motivated by "zomg, something to chew" than obeying the 'target' command

We'll see if I can get a repeat performance this evening (it's midday and he seems to be snoozing - it's normal for young cockatiels to snooze at midday right? Right? /paranoid).
Anyway, I agree with starting training as soon as the bird seems ready. It seems like a positive experience for both bird and owner. Barney had almost as much fun as I did.