Guild Wars 2: Account linking and you [Updated]

You are surely aware that Guild Wars 2 is nearing its headstart and launch dates. You might also know that players of both Guild Wars and Guild Wars 2 have a bit of incentive to link their accounts. The Massively team has been getting a fair few questions about the ins and outs of account linking, so this here is a bit of a knowledge dump that'll hopefully sort out some problems.