Don't tell people that their time is worthless
Which means that I've been pitched by other authors for a variety of marketing requests: set up a signing in a bookstore, write an article, provide them with posts on a large social media network that I managed, or other similar promotions for new titles.
All of these pitches invariably started with "This won't cost you anything."
I would respond, nicely, "Well, it always costs staff time, mine or someone else's at [insert current company of employment here] at the very least."
Most of the time, the response was: "Exactly. It's free for you and will help me sell more books, which are really, really good by the way. If I sell [x amount], then I will [publicize your website, donate to your cause, pay you something]."
Because I like authors and I like books, I would try this gentle response: "So you're asking me [and my company] to provide you with marketing for your books in return for a future [payment, donation, goodwill]. Instead of a promise that you'll maybe do something in the future, are you willing to sign a contract stating that you will [provide publicity, bring x number of people in the store, write an article to our specifications, spend your time on this]?"
At this point the author tells me how much their time is worth so they can't be expected to do any work before the event as well as other reasons that they can't sign an actual contract that would hold them to fulfilling any promise made.
To which my final suggestion has evolved into "Well, send me a press release. I'll try to find a place to publish it." I will too. It might just be a tweet on my personal account or it might go into something larger. It's as much as I can do with my "free" time. A few follow up but lots never do.
Now I should emphasize that these conversations always take place with strangers. People who don't know me at all but feel confident in telling me that my time is not worth as much as their time. They may be right (about their time being more valuable because they are writing the one true book that will solve all problems everywhere) ... but I have found over the years that telling somebody that they are worthless is not a great way to get them to do you a favor.
If you're calling to pitch a bookstore, a blogger, or anyone else, try the pitch on yourself and friends first. Ask if it seems like you're demanding a service or requesting a favor (there's a difference). See if you can show how you can help the bookstore, the blogger, or other achieve their goals (which may not be selling your books) by partnering with you. It helps if you demonstrate some knowledge of what they do as well as talk up what you have done.
Write, publish, have fun with your books, be successful. That is my wish for all authors. Hope these tips help.