The rise of mobile viewing platforms means TV stations have new tools to offer advertisers who want to reach viewers no matter where they are. And it means stations can offer a greater variety of options — and price points — to potential advertisers, many of whom don’t buy time on traditional TV. This is Part I of a four-part series. Part II on the automated buying of spot will appear tomorrow; Part III on Thursday will focus on improving digital sales operations; and Part IV on Friday will offer a case study of a successful digital sales effort and the lessons it offers for broadcasters and newspapers alike.