For Cancellation of removal you need a few things like:
1) Good moral character
2) 10 years in US prior to being placed into removal proceedings
3) USC or LPR, Parent, Spouse, or Child who'd suffer "EXCEPTIONAL AND UNUSUALLY EXTREME" Hardship from your removal.

Thing is:
1) COR cases are EXTREMELY LONG and EXTREMELY HARD. If you're claiming via child the child will probably turn 21 before you're granted COR. If you entered on a visa you'll at that point probably just file for termination so you can AOS.
2) COR can only be sought while in removal proceedings. So you can't just file a form like for Asylum. You need to end up in removal proceedings. That's when you file EOIR-42B, and when you get the receipt you file an AOS packet with USCIS so you can get a work permit while the case is pending.
3) There is a limit of 4,000 green cards that can be granted via COR per year. That quota goes fast. So don't be surprised when the judge tells you to come back next year for a hearing. No one even knows what the backlog is. No one even knows if there is a wait list to begin with or is it a First Come First Serve basis.

On the flip-side COR can overcome a permanent bar for illegal re-entry, and some others. It cannot overcome a false claim to citizenship.

Basically I'd treat it as something to do as a last resort when you have a solid case (kids make for solid cases, especially if you didn't teach them the language of wherever you're from, and if you come from a racially homogeneous country and your kids are mixed (e.g. you're white from a 99.9% white place like Poland or Ukraine and your kids are half-Asian)).
Not just loitering in front of the local ICE office wearing a sombrero and playing the maracas on your 10 year anniversary in the US. Though I guess if you want to end in removal proceedings that's one way to do it.