Just be willing to walk and mindful of the period of non-renewal notice as stipulated in your contract - and also means by which notification is accepted. Some contracts require written notification sent through registered mail. Also don't be afraid of shopping for networks, find out what competitors are offering and begin talking or forming friendships, the more public the better. I renegotiated with another network earlier this year, and it ended up going well. I was nervous AF when trying but knew what I deserved and went in near the end.
When it comes time to renegotiate be adamant on your ability to leave. You might get low-balled with a 70/30 that's just wasting your time. No music library is worth that much. Also be mindful of how much money you're leaving on the table by letting it linger or taking another offer; this basically means considering potential revenue you might be missing out if you let your current contract slide til the end or if you take a deal right after. See how the talk plays out. They might let you go, which isn't a bad thing. There are so many networks out there right now it really is a content creator's market, if you reframe it as that. You're literally holding all the cards.