I spent 7 hours with Catsuki day one. =[
Try watching some videos of high level play. It'll give you an idea of how you should be moving. Especially against a Nero, who can REALLY restrict your options. If at any point you're not sure what you should do, you should probably block. Get on IRC and get a few games going against random people over netplay and save those replays. Then you can replay it later and think about what you could have done to not get hit.