Come up with what minimum valuation you’d be happy with but never share that number with any investor. If the number is too low, you’ve set a low ceiling. If your number is too high, you scare people off. Just like on eBay, you only get to your desired price by starting lower and getting a competitive process going. When people ask about price, simply tell them your last round post-money valuation and talk about the progress you’ve made since then.