The general rule of thumb for bitcoin security is to manage your own private keys and not keep your coins stored on an exchange. Active traders end up taking that risk because we need the liquidity of centralized exchanges. If you are trading on an exchange there are ways that can help reduce your risk exposure.
Here’s a list of 4 ways to reduce third party risk:
#1 Keep Reserves
Only trade with a percentage of your overall holdings. If an exchange goes bust and you lose your coins then you won’t be wiped out of the game. Personally, I only trade with 20-30% of my holdings and use leverage to increase my trades.
Make sure to research any exchange before using them. When traders experience problems they tend to bring it to public attention to warn others. Social media site like bitcointalk.com and reddit.com have up to date information.