I've developed bipolar disorder. What should I be watching out for in the future?

Stability! Work closely with your doctor to find the medications that work for you. And, looking back, try to identify the earliest symptoms that you can when it started to go bad. The earlier you can let your doc know you're not right, the faster you 2 can get you back into balance.
Sleep,target symptom. Know your illness and try to accept it as best you can. Being compliant with your treatment - both medications and psychotherapy is a great start as well. See yourself as a partner in treatment and freely ask questions and propose solutions as you see fit. Sleep hygiene is critical. Knowing your target symptoms - what are the early signs of recurrent hypomania or depression - and reporting them.