Back things up. Seriously. And I'm not talking about computers crashing or losing your drafts. No, I'm talking about losing your characters. No, not the letters, or words, although they do contain the necessary information.
No, somewhere down the line you're going to realize that those raw feelings you initially had towards your main characters got lost. Tainted by later edits when you got worried about them looking stupid, afraid, or downright ugly. So save them. Save them ALL.
I'm facing edits right now that have me jumping back to some VERY early drafts (which I'm SO glad I kept). Strange how I would edit my heart out and then find myself back at square one again. But it's real. Because the writing and feelings were real. Fear. Angst. And characterization that hadn't been beautified by my later impression of who they became or how they'd been changed. The dialogue and wording are improved of course, but the raw emotions came from the first draft.
I need those. So I need my back ups.