0% APR first 12 months on new credit card. Can I exceed that 30% rule of thumb and not hurt my credit score?
Your utilization ratio history is irrelevant to its impact on your credit score.  If you run up 80% of your utilization In January, then pay it back to 10% in March, your score in March will reflect the new reduced ratio with no memory of the 80% utilization last month. With that said, don't go around overspending just because you have 0% apr for a little bit.  Spend what you would spend with cash.