First and foremost is knowing what you want in a MH and what your willing to spend. Research available bank or credit union rates and terms before looking. Research what you want to look at, and the prices they're selling at or worth.
This way you have something to stand on when they start the conversation. If it doesn't fit your needs or expectations or the pressure is turned up, just get up and leave. If you aren't ready to buy don't give them your ID, they might run a credit report on you. Don't be in a hurry to buy. If you let them control the pace, it's to their advantage.