I’ll keep this short and to the point.

- Don’t participate
- Don’t participate at a level to receive full employer match
- If automatically enrolled upon employment stay at the initial percentage level and investment funds
- Take loans and hardship withdrawals
- Panic on stock market dips and lock in your losses
- Don’t diversify your investments. Using two different large cap index funds is not diversification
- Take too little or too much investment risk for your age
- Don’t rebalance your investment mix periodically
- Ignore fees and other costs, especially if you rollover funds to an IRA
- Don’t take advantage of the Roth option if available, at least for a portion your contributions