4. Have something worth selling.
Everybody is selling something. It might be an item, a service, a download, an idea, or a worthwhile cause.
Whatever you're selling, it's got to be worthy of the cost. (And always remember that reader attention is an essential item that's in strictly restricted supply.).
Whether you're requesting dollars, euros, yen, or valuable time and attention, you've got to offer something that towers above your asking rate.