i'm building up my next set too, but not before some practise on some others =]
kudos to you
To be honest it might be a waste of time to practice on others. I'm not sure how you can really destroy any of the components by screwing up. On top of that, just double check everything after every step. Everyone has their wheel building guide preference, but our master tech just handed me Barnett's guide, and honestly it worked really well. I read through it once and then worked as I read the second time and it looks like it worked out fine.