Well.. we were destroyed and it looks bleak. Of course, things looked bleak for the Republicans 2 years ago, so things can change quickly. Everyone has their post-mortem, What we are looking at is a rapid Republican Congress and we should use that to our advantage. Things need to change in many ways at the local, state, and national level for us to have a chance (example- we need to win state elections to undo gerrymandering- easier said than done)
Here is my playbook
1) President Obama should encourage Republicans to pass laws. Use the fact that they control Congress to their advantage. He should in fact dare them to vote to wipe out the Affordable Care Act. Likely they won't put their money where their mouth is. If they pass piecemeal bills to eliminate portions of it, then he should veto and tell them he would consider passing their bills if they offer an alternative. We all know, an alternative will never actually come.
At the same time, the millions who were insured need to speak up and protest as loudly as the Tea Baggers did in 2009, to protect their healthcare. (this may not work because tea baggers yell louder and get tv coverage).
Regardless, the key is to challenge them to pass laws. If in a year, the Republicans offer no viable law to replace the ACA, or do not offer an immigration strategy, throw it in their face.
2) Refresh the party. Who are our leaders? If you look at a roster of the Senate, of the Democrats that are left standing, many are getting up there in years. We need to encourage the "safe" ones to step aside. (Schumer, Boxer, Feinstein, etc). Granted, nobody likes giving up power but we need young blood and a change in the power structure
3) related- encourage Hilary not to run. She will do what she wants and I realize this is contraversial. She may be our best home in 2016. Then again, she is a behemoth in name and fundraising that is near impossible to overcome and more importantly, discourages debate and fresh ideas. If she is a fait accompli, the party will suffer
4) Support marijuana legalization and other issues involving individual rights. Marijuana reform is controversial but if not adopted by the Democratic party, the Rand Pauls will flank and make it a Right wing issue- which will take young voters away from the party
5) Find a leader who can lead and who has vision. Dean probably won't do it again. It is somewhat of a thankless job. But, it is needed. Moreover, it needs to happen on a local level. Win the state house and it is easier to take the House. Lose it , and we deal with threats to split up electoral votes
Bonus
6) convince bright minds like Sherrod Brown or Elizabeth Warren to run. Only knock on Warren is the stereotype that she is a "massachusetts liberal" and given Kerry and Dukakis's record, it is an unfortunate label. Hye, maybe she can change states like Scott Brown?? :)