Do your own research, don't do this if you don't know anything about options etc etc etc, but If you're concerned about a huge market crash (like I kind of am) here's what I'm doing:
In addition to your regular portfolio distribution, Buy long expiration UVXY puts. UVXY tracks volatility futures. Higher the volatility, higher UVXY price. A put gives you the option to sell shares by a certain date. ETNs that long volatility tend to decay like crazy, buying puts makes this work in your favor so it's not so expensive to hold long. This step is optional, I just like the collecting a premium off the vicious decay while I wait for the "real opportunity".
Now at some point we'll probably encounter some kind of crisis that'll make your long expiration UVXY puts look terrible if you've got any. This is when you buy even more, short expiration UVXY puts. (Weeklies and monthlies.) When the crisis passes, your short term weeklies should be worth quite a bit of money and your long terms will have recovered as well.
You'll have to learn about cotango/backwardation to get a robust execution strategy, but my heuristic is to start building a small position when the VIX is 14, and if the vix gets to 20 start going hard on those monthlies. If "the big one" hits we could see the VIX get to 50+, so if you're guarding that maybe fewer weeklies and more monthlies. :P