Quote by RejectReality
Temper your expectations for anything long enough to consider breaking up, and especially anything over 10k words. The Lush readership trends sharply toward shorter pieces. Which isn't a bad thing, because most of the other sites trend sharply in the other direction. Having a place where shorter work gets a fair/preferred shake is a welcome arrow in the quiver.

If you do break it up, don't draw out the releases. As soon as one is approved, put the next part in the queue. The natural bleed of readers to progressive parts will only increase with time between submissions. That means having the complete story ready to roll before you submit part 1. You don't want to get into a situation where life intrudes and prevents you from delivering the ending in a timely manner.

Give some consideration to potentially triggering content that will appear in later parts of the story. If there's anything coming later that you think might make readers squeamish, you might consider coding for it with part one, or perhaps utilizing the author note section, or both. ( Describing that the tags are there for later parts of the story ) Little will make readers balk more than starting something and feeling as if they were blindsided by the later parts when they appear. They not only back away from that story, they think twice before opening the next submission they see from you.

Let readers know up front how many parts to expect. Add 1 of 3 to the title, or leave an author's note saying how many chapters there will be. If it was originally written as a single story, and not written as a serialized story from the beginning, "Part x of x" is probably the better strategy. This is especially true if any of your break points don't feel like an ending to a chapter. Readers have a different mindset when they see "part" as opposed to "chapter"

Off the top of my head.