You want to diversify. So, if you have a significant portion of your money invested in a startup, I think you would want to be a lot more conservative with the rest of your money. You can real safe with bonds or cds. I also look for old, boring mutual funds, that have been around a long time, and get good performance.

Although, I haven't gotten around to implementing it, I think there could be a powerful concept, which I'll personal hedging. The idea is to think of your investment as a hedge against the costs of things you want to buy in the future. So, suppose you are investing to retire. 1) Track your expenses 2) Figure out what your expenses will be when you retire. 3) Buy proportional share of the value chain for all the companies you will buy stuff from. Presumably, you want it waited to cover all your expenses. Now, this can get tricky because you may spend a lot of money with companies that aren't public, and some industries may be in a bubble. Further, you will have to shift your investments to reflect industry shakeups. For example, if you change your mind about what products you like, you would also change your portfolio. Industry changes would also affect, who in the value chain gets the profits, and conglomerates or weird capital structures can make this a bit tricky, but I think it is a powerful concept.