I told people that I was going to do my own practice, even my previous boss. Luckily I get my first client with my previuos boss' help. I hope that I can get refer by the first client. For tax clients, I am going to do some ad on Chinese newspaper and forum.
My coworkers, one started his own practice to do tax preparation after seven years working for small CPA firm. He had clients before he left firm. Another girl started her practice to do bookkeeping and has 5 clients, which is enough for one person practice. You have worked for same firm for ten years. If you start your own, probably some clients will go with you.