This is pretty easy:
1. Downplay social issues and focus primarily on economic ones. Only mention social issues when asked about them. The religious/social conservatives are already safely in the GOP column and will probably stay there as long as Republicans don't radically change their positions.
2. Improve minority outreach, especially to blacks and Hispanics. Spend more money on advertising in Spanish and highlighting our party's history of fighting for civil rights against Democrat opposition. Also explain why welfare reform is good for minority communities and emphasize support for school choice.
3. Stop "RINO hunting" and infighting between factions. Become more of a tolerant, big-tent party that accepts members who agree with basic core principles.
4. Most Important: Explain why conservative values are better for ALL Americans than the current liberal consensus.
Strategically - fully agree. But tactically - there can be substantial losses, while process will go, with a lot of social conservatives not voting or voting 3rd party. BTW - it seems to me the process is already going, at least - on WEB sites: when i look at "issues" pages of Republican candidates this year i seldom see anything about "abortions" or "gay marriage". At the height of tea-party movement in 2010 it was almost obligatory... This year it's almost exclusively about economy, finances and ACA..
