Advance Against Royalties.
Publisher shall pay to Author, as a non-refundable advance (the "Advance") against and on account of all royalties and other sums accruing to Author under this Agreement, the sum of _____________________ ($_________), payable as follows:
$________ on the execution of this Agreement;
$________ on acceptance of the complete manuscript of the Work; and
$________ on Publisher's initial publication of the Work or within _____ months after acceptance, whichever comes earlier.
Today, publishers insist on paying the advance in installments, rather than all upfront. Milestones for triggering payment of an installment include signing of the agreement, partial manuscript delivery, publisher's acceptance of the manuscript, publication, publication of a paperback edition, or simply a year after publication.
In recent years, payments split into three, four, and even five installments have become common. For advances of $40,000 or less, try to negotiate to receive the full amount in two equal installments; and for advances of $40,000–75,000, no more than three installments. For larger advances, publishers may insist on holding a fourth or fifth installment back until publication of the paperback edition or 12-18 months after initial publication, whichever is earlier. Ideally, all advances should be paid in three installments or fewer, or a year after initial publication of the book.
The Authors Guild believes that this kind of delayed payment of the advance is unfair to the author, who needs the advance to conduct research and to pay living expenses while writing the book. When most of the advance is paid after delivery or even publication, it can no longer be considered an advance. Most authors have to juggle different jobs in order to write a book where most of the "advance" comes well after the hard work of writing is done.
Many publishers provide for "acceptance of a satisfactory manuscript" as an event triggering payment, rather than delivery of the manuscript; delivery is vastly preferable since the timing of acceptance is in the publisher's control. Most publishers will insist on acceptance as a trigger, however, to protect themselves in case the manuscript is not satisfactory.
To avoid long payment delays, you should make sure the publisher has a limited amount of time to accept the manuscript or respond with specific comments (as described in Section 7). Alternatively, you can try to include a provision that simply requires the publisher to pay you within a fixed period after delivery of the complete manuscript (unless it is properly rejected under the terms of the contract). The same goes for payment of any installment due upon publication. For example, try to modify the installment on publication language to say "publication or within  months after acceptance, whichever comes earlier." This will ensure that you get the final payment even if publication is delayed.
Your agent will negotiate the advance. If you don't have an agent, you can try to learn the publisher's projected first-year sales and expected retail list price, which the publisher may use to calculate and factor into its offer. Sometimes the author's share of projected first-year subsidiary rights income is also factored into the advance. Advances can vary considerably, however, depending on additional factors, such as the financial resources available to the publisher, your reputation as an author, the success of your last book, the subject matter, the audience, and the illustrator's reputation (for children's books).