This is a great question, and I happen to have experience in this area from being a campaign manager for some different candidates! As to qualifications, every state government runs similarly in that the executive branch is co-equal to the legislative branch. The first qualification for a state campaign is a person with experience in dealing with the legislative branch. The ideal person would come from either the state house or senate. A state position like a governorship often is seen as a stepping stone to a federal Senate seat or as potentially a presidential candidacy. Mayors sometimes fit the bill if they have a statewide reputation, but that is often not the case. In today's elections, though a lot of attention is paid to candidates who claim they are not politicians and that their background is outside of government (in business, for example), it is unusual for a candidate for governor to not have significant political connections.
Campaign strategy generally is divided into two areas. The first is the message. Message, in modern campaigns, is driven by polling data and by trying to paint a negative picture of your opponent. The second part of the strategy is voter turnout. The techniques for increasing voter turnout are numerous but include campaign materials, marketing, and other, more technical components.
The third part of your question deals with the internal perception by voters of both the candidate themselves and how much the candidate appears to care about the issues that matter to the voters. Voters don't necessarily vote for someone as much as they vote against someone. Thus, a successful candidate has to project empathy for a diverse group of voters.
The last question involves the personal drive and motivation of a candidate. Campaigning is grueling. Candidates and their families come under a great deal of scrutiny and attack, much of it very personal. A candidate must be willing to subject themselves to the attacks, present a positive image, and sacrifice personal security. Candidates will spend a lot of their funds to campaign, potentially requiring them to mortgage their homes and go without a paycheck during the time they are running for elected office. Fundraising is critical, and the law only allows for reimbursement of campaign expenses, not personal expenses like groceries, mortgages, or loan payments. This is why many candidates who run for statewide positions are wealthy. They are the only ones who can afford to make a financial sacrifice.