Caveat: I am far from the expert on this (your agent should be!) but here are some of the things your agent will consider when negotiating/evaluating an offer, that you should bear in mind when reviewing/asking questions.
World rights/Translation rights: many publishers like to make a rights grab right out the gate, and most agents will try to retain them, especially if their agency has a strong in-house sub-rights team. There can be pros to having world rights via your publisher, especially if they are a major player with established imprints in major territories/strong relationships with foreign publishers... but if your agent/cy IS great at foreign rights sales, it's in your ultimate best interest to retain rights, as they can often negotiate better deals piece meal which ultimately will bring you more money and possible royalties. There's a lot of variation within this umbrella that your agent will understand/deal with.
Audio rights: another one publishers love to snap up and hold onto. There are pros and cons to it as with world rights. Sometimes they'll retain them for a certain amount of time and then they'll revert back to you so your agent can sell them themselves if the publishers doesn't.
Payment terms: I understand these nuances the least. This is why I have a literary agent who is smart and good at her job, ha. So the best I can offer is: there are LOTS of variations and nuances not only to what you are paid but HOW. And your agent will negotiate to get you favorable terms. Ask questions.
Royalty rates: This is a big one. While most books don't earn out their advances, if you DO, you want to have fair and favorable royalty rates. I can't tell you what's good vs. bad, but again: this is why you want a GOOD agent in your corner, one who is good with numbers/money/negotiating.
Notice the theme? This is where having an experienced, competent, stalwart agent is PARAMOUNT. This is why, when you are querying and considering offers (should you have multiple), you should consider aspects beyond personality/editorial/relationships–those things are important for your working relationship and getting a deal, but you should also want someone who is really good at negotiating and contracts (or whose agency is).
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#HowToAuthor: Agents & SubmissionNon-Fiction
Advice for writing book-shaped things and getting them traditionally published. This series will cover everything from querying to agent fit, to building a platform and marketing yourself.