Preparation - a Frank Discussion
For the bipolar individual - although you may struggle to remember every detail of what happened during periods of illness, you likely are one of the best people to know how you may appear when you begin to display symptoms. Striking a balance is difficult but vital, it's important to make sure the friend knows what could potentially occur, but it is equally important not to make them panic unnecessarily. It could be useful to come up with a checklist of warning signs - you could organize these by which order they might appear, or you may find creating a table with 'traffic light' coding is useful. Your doctor or relevant clinician could give important and useful input into this, as they may notice signs that you may not.
For the friend - learning what might happen should an episode occur may be distressing at first, but it is important for the future. Ask for honesty and clarity from your friend, and see if you can create a document with them to help you recognize any issues arising. Feel free to ask (sensitively worded) questions about what might happen, it's always better than making assumptions.
Forgiveness & Understanding
For the bipolar individual - following on from an episode, you may react with embarrassment, or you may feel as though you should not seek forgiveness from those who you might have hurt, or affected negatively, as this stems from an illness. It is important to try and see things from the other side though, and realize how your behaviour might have impacted someone else. If you feel your friend is not being understanding at all, it is important that you address this and have an honest discussion with them.
For the friend - repairing the damage we've caused after an episode is one of the hardest things to face. Bipolar behaviour (such as hypersexuality, excessive spending, self harm, and grandiose delusions) is something that is hard for both parties to come to terms with, and it is useful for you to try and be as understanding as you can of the embarrassment we may feel afterwards.
Respecting Boundaries
For the bipolar individual - boundaries can seem wobbly, distant, or even invisible to us at times - especially during a manic episode. However it is important to respect the boundaries of your friends; e.g. don't call them multiple times in the middle of the night, don't expect them to think all the brilliant ideas that might suddenly occur to you are necessarily safe or a wise idea, and if you are feeling hypersexual, do not make advances on them, or their partners.