As what the GOP needs to do… I see 2 things.
First, stop putting forward the more extreme people in your party to run. Not so much Romney as he’s a moderate (I’ll address that in #2), but they had several people running for the US Senate that were way to the right. They had no broad base appeal. Now, they may when things get worse, but for now select more centrist candidates.
Second, the left’s path to victory was lie, hate and divide. And it worked great. The GOP needed to confront that crap more, but failed to do so. The left operates out of the “you can fool some of the people…” philosophy and it has been deadly effective until things get so bad people stop believing them. But that only lasts for a short time. So the GOP needs to either fight fire with fire (not recommended, but it has been effective for the left), or get out there more and win some votes. I think the GOP is missing many votes because they don’t appeal for them the same way the left does. If they made it a point to take their side to women and minorities more, the left’s lies will start to being believed a bit less and the GOP can stabilize their base more.
The democrats are far superior campaigners. Better strategy, they connect better with people so their sound bites initially carry more weight. And, they are far more passionate than the right. And they communicate better. Those are all lessons the right needs to learn from if they want to become players again.