Saving for retirement can be a challenge, but it's important to contribute as much as you can to your company's retirement plan. Some companies also offer a Voluntary Retirement Account that can be rolled over into a Roth IRA after retirement. If you're lucky enough to have that option, CNBC personal finance expert Carmen Wong Ulrich recommends taking advantage of it. The best part about this is that the money you roll into the IRA should be post-tax dollars, so you won't have to pay taxes as you withdraw it. Watch the video to see Carmen explain.