What helped your putting go to the next level?

As long as I can remember I've been an incredibly average putter. Some days great, other horrible. But I'm really looking to put in the time to take that next step this year.

What drills have you done specifically that made your putting go to the next level? Even any mental changes with reading greens or simple grip changes would be great to know before I go tinker away.

There are so many aids, drill and mental coach videos out there that it can get a bit overwhelming to ones that are actually worth your time.