Is it "Chapter One" or "Chapter 1"?
Chapter 1. As someone who has written stories with over 100 chapters, I don't wanna have to write out "Chapter One Hundred Seventy-Seven" in words LOL.
If you have more than one scene in a chapter, how do you split them up?
I use *** for scene breaks. Or, as Text to Speech man would say, "Asterisk asterisk asterisk" LMAO. Is that what you're asking?
If you want to designate that something is a flashback or happened in the past, how do you designate it?
I write ~*~*~*~*~*~fLAsHbAcK!1!~*~*~*~*~*~*~
LOL Actually, I just put it in italics.
Bold, italics, or underlining?
I use italics for words that are emphasized in dialogue, as well as inner thoughts and flashbacks or dream sequences. I don't use bold much other than for chapter titles and when describing what signs say. I don't really use underlining in fanfics.