I've been trying to get traditionally published for a year now, contacting agents and the odd publisher who accepts unsolicited queries. But it has dawned on me that if my manuscript were to catch someone's interest I have NO idea of how to handle the next part. None at all.

What are the basics to look out for when negotiating with publishers? What are the red flags, or the must-haves on my end of things?

(Note, I am contacting agents in multiple English-speaking countries, and making the odd attempt to get published in non-English speaking ones)