Should I invest my IRA in gold? If so, what percentage of my portfolio should it be in?

From my perspective. the only viable way to own gold in an IRA is to own an Exchange Traded Fund (ETF) backed by physical gold. You can find such ETF's through a search at www.etf.com.

Among the drawbacks to ownership of the "physical" are the storage costs charged by the dealers who advertise gold IRA's, the liquidity at a fair price for trading, and the mechanics involved with taking a Required Minimum Distribution from IRA's heavily invested in the "physical". If you are determined to own gold, check the websites of the major precious metal dealers offering gold IRA's. Be sure to check their storage charges among other costs of their offerings. Add that cost to "carry" the position in gold to the move up in price you'll needed for the trade to be profitable.

As to the "percentage", for years I have used portfolio management techniques and recommendations from Dorsey Wright & Associates. In their dynamic allocations currently, there is no exposure to gold or any other commodity among the six major assset classses they work with (domestic equity, international equity, fixed income, cash, currencies,, and commodities).

The oddity I see in the current markets is the failure of gold to hold its long held "safe haven" or "crisis asset" status. There has been no rally in the price of gold since August-December of 2012. I venture to say there have been numerous crises since then but they all have failed to move the price of gold upward for any sustained period of time.

My opinions, but I think that's what you asked for.