If I were Stephen Harper, the very short answer is that I'd want to govern for two years and bring in the top five priorities I've campaigned on. When you've produced a list the way he has, it is what the electorate expects you to do, and when you've done it, you've succeeded. Those five would also be reasonably popular and a focus on them would further establish centrist appeal for Harper.
How can he do this? Political Staples has one review of the possibilities. Another way is to work out a deal with the NDP as below.
Once he's passed his top five, Harper needs to look for the right opportunity to go back to the polls and run on his record, but that will depend a lot on other events that occur in the meantime.
If I'm Jack Layton, I'm happy but I know things just get trickier from here. Having more Members of Parliament is nice but the point of a political party is to, well, "get results for people".
Jack needs to ask himself where he wants to be after the next election. I think the answer is 40 seats in another minority. That would spell success, as far as I'm concerned. So, how can he get that and what does he want to acheive along the way?
One route is to make a deal with the Conservatives. The most attractive way to make a deal would be to say they will help the Cons pass all of their 5 priorities, at a price. So then, what can the NDP get that would make it worth their while?
The list would likely need to include more than this in terms of promises of what the Cons wouldn't try to do with other parties. I'd suggest getting it in writing -- from Stephen Harper, not Peter MacKay!
For this they'd be promising to support the Conservatives on their 5 priorities plus not vote to bring down the government for a specified time period (maybe 2 years).
Although the NDP doesn't have enough support to guarantee passage of anything, I believe a deal between the two parties would certainly have the moral authority to expect success in governing. If these two can work out a deal for stable government, I wouldn't want it stopped by separatists or a defeated party with no leader.
What the Conservatives get out of it is a nice record to run on in 2008, and the ability to avoid having an election at a time chosen by the next Liberal leader. The NDP gets to continue to show themselves to be useful, and makes a case for winning even more seats, particularly in Canadian cities.
Reunite the party. Pick a new leader. Build a war chest. Figure out how to take Canada in a direction that will be even better than what the Conservatives and NDP can do.
Pick a seat you can win. Start working on it now. But don't stop increasing your nationwide vote total.
Whatever. Someone else can write this one.