I think this approach is underrated and can highly recommend it.

If you are an engineer and you keep your living expenses low, you can most likely survive doing consulting/contracting for 1 day per week, leaving you the rest of the week to work on your startup. This minimizes your financial risk and leaves your savings intact, leaving you only with the opportunity costs (but if you are worried about those, you probably shouldn't be doing a startup in the first place).

Additionally this lowers the pressure to find investors quickly (or at all) and gives you the time to build something great.

Another one that I didnt included that I've actually written about is selling a business on your product or service before building anything. http://ryansrich.com/blog/step-one-acquire-customer.html