This is a great subject for the forum. Like many, I played for many years using just my index and middle fingers having learned "pattern picking" from early Happy Traum & Stefan Grossman books in the 70s. But I was able to add my ring finger to my playing based on a tip and help from Leo Kottke who I got to know back in the 90s.
Since my youth I had, again, played only with my index and middle finger and planted my ring finger on the guitar top while doing so. I was showing Leo how I thought he played one his tunes (having tabbed it out) and he stopped me and said (in so many words), "Uh, you really need to start using your ring finger too you know. And to stop planting your ring finger on the top." Then he told me, "I used to do the same and some guy told me to do this. Take your ring finger off the top and rest it on the 1st string just like you do the top. And at first it's okay to lift your ring finger up and play that first string with your middle finger, but after a while you can start using the ring finger."
In short, he said that planting the ring finger on the top helped some to "steady their hand." But it also precluded the use of the ring finger in playing. By planting the ring finger on the 1st string you could still get that "steady hand" feel but be able to use the ring finger to also play full four-finger chords or arpeggios at once (T, I, M, R). And while it took me a while to do so, the technique worked.
Admittedly, being at best an intermediate "bedroom" player, I still primarily use the I and M fingers but on some tunes, being able to comfortably use the ring finger *really* helps. Chet's first section after the intro to "Heartaches" comes to mind as a tune where the ring finger helps a lot. And there are countless more.
Jim Jarrell
DeLand, FL
www.tabpigs.org