1st When challenging a incumbent you need to start the primary earlier so you can pull together sooner. Obama had months of additional prep and advertising as he watched the Republicans beat up on each other. Even if we had just ended it 2 months sooner that would have allowed 2 more months to get ready for the general election. Every bit of organizing that can be done earlier should be.
2nd Republicans need a deeper ground game at all times but especially when facing a incumbent. Obama had a ground game mostly still set up from 2008. Republicans hoped that the excitement gap would push them over the top but it fell just short. The RNC should great a deep and rich ground game so no matter who is runner at what ever level they do no need to put time into creating a ground network it will already be there. The ground game needs to be three levels deep before Republicans even pick a candidate. The RNC will have to take the lead to create this as the DNC has a ground game advantage as of today.
3rd Its clear you can't count on cable news media to get your message out. Republicans need to work local news networks and build a deep conversation around the 3 talking heads of CBS, CNN, and MSNBC. Start at the local media level of Radio, TV, and what News Papers are around and than move to blogs, and local free papers. You can feed them stories they will be excited for the attention offered. Dominating the local story is their best hope to get the message out. I'm not talking about a few interviews or a letter sent to the op-ed section. I'm talking about a army of representatives appearing for weekly interviews and phone calls. So that local population knows them by name and identifies with them.
Now one for everyone. This was so close in many states. Never again can you say your vote never counts. Just like you can never say debates don't matter.