Well, I'm not qualified to give advice, but in my opinion:
1. Stay away from instruments that take big plunges up and down: NO PHARMA, beware cutting-edge tech. One move against you, and you're deep in the red for months with dead money, or you have to dump and take the loss. Also avoid smaller companies; say, less than 1B in market cap. These companies either get bought out, or crushed when a big player starts giving away what they have for free. It can be great news, or not--depending if you're long or short. Regardless, you're after the swing--not a big hit.
2. Stick with instruments that:
a. Have market cap of 1B or more. Download the company list spreadsheets from the Nasdaq at the link below, and you can sort
http://www.nasdaq.com/screening/company-list.aspx
b. Those that have a well-defined market share
c. Have a steady revenue stream that's based on a clear and reliable demand.
c. Instruments that swing up and down throughout the week, but don't stray too far from their average price.
d. Utilities were pretty good for this. I just poked around a bit, and found the New York Water Company (Nasdaq:YORW). Pretty boring, and with speculation anything can happen, but it has a reasonably predictable swing. No question about it: people need water.