I have to agree with lydelia, and it's not flippant, it's a serious thing to be in violation of a lease. A lease is a contract between tenant and landlord, outlining the rights and responsibilites of both parties. If a tenant violates the lease, that means the contract has been breached, and the landlord is not held to his end of the contract, either. You forfeit your rights outlined in the lease when you breach it. So, as lydelia said, you could be faced with eviction with very little time to get out and no refund on your deposit.
Lots of people do it and get away with it. I just wanted to make you aware of the position you put yourself in if you don't. So you say you wanted tips to help you keep your animals. Then lydelia gave the best tip of all -- rent from a landlord who allows pets. Sorry, but that's just good advice.