- Remove your most precious info from online accounts (e.g. everything in the real world, such as your physical address). Use PO boxes / mail forwarding / etc. for that

- Create a new, anonymous email account and use that for accounts that you care about to minimize the chance of successful social engineering attacks

- Depending on how serious this is and how much the hacker knows, consider warning your friends and maybe even colleagues about the situation

- Obviously don't have anything visible to friends-of-friends or to the public on facebook, remove your public photos especially those that can be photoshopped into a fake id, etc.

I'm not an expert in this, just some ideas.