How should Christians vote?

Many Christians at election season scratch their head and wonder exactly what sort of principles are to guide them as they face the ballot box.

Letter from America Josh Moody

This is particularly true at this election season, not only in the UK with 'Brexit' but also in America as citizens here begin to face up to the likely options that they will have on the table. What does it mean for a Christian to vote his or her conscience? What sort of guidelines can be given regarding voting that do not stray over the line of partisanship?