I don't think the answer is to learn a lot of patterns or read a lot of tab. I tried that twenty years ago and got so screwed up I almost quit.
When I was studying karate years ago the people I trained with used to say stuff like, "I'd rather have one technique I can fight with instead of ten techniques that fight me" and, "It's a lot smarter to learn one technique and explore twenty-four ways to use it than to learn twenty-four separate movements".
An example of this sort of thinking can be found in frailing banjo. In frailing you have a basic picking pattern made up of a quarter note and two eighth notes. In the hands of an experienced frailer that core picking technique can be twisted into some pretty cool stuff. The brilliant thing about frailing is that the core technique is so freaking logical that the average student can pick it up in the space of a few hours.
I'm not kidding. If you can play the basic frailing strum and make two chords (not counting the open G chord) you can be playing and singing folk songs in an afternoon. You don't see that done much today simply because people have made a business out of complicating this stuff.
The crazy thing about fingerstyle guitar and frailing banjo is that the two instruments/styles share a similar core technique. This makes sense when you figure that the banjo started out as a homemade instrument that anybody could build from parts gathered in any back yard. When cheap guitars became available people could switch to a more modern "store bought" instrument that had more flexibility than the old five-string.
So the frailing strum on the banjo: D---0--0-----------0--0-----|-| B------0--------------0-----|-| G------0--------------0-----|-| D------0--------------0-----|-| G--------0--------------0---|-| m m t m m t
(pick down with the middle fingernail on a string, brush down across the strings with the middle fingernail and pick the fifth string with your thumb. The rhythm is a quarter note and two eighth notes giving you a count of "one two and three four and" for each measure.)
turned into the "Carter strum on the guitar: C |------0-0------0-0--|-| |------1--------1----|-| |------0--------0----|-| |------2-----2--2----|-| |---3--3--------3----|-| |------x--------x----|-| t t i t t i
(Strike/pick down with the thumb, brush down across the strings with the thumb and pick up with the index finger.he rhythm is a quarter note and two eighth notes giving you a count of "one two and three four and" for each measure.)
That's the basic frameworks. If you break that initial quarter note in half you wind up with a string of eighth notes: C |--------0-0--------0-0--|-| |--------1-------1--1----|-| |--------0----------0----|-| |-----2--2-----2----2----|-| |---3----3----------3----|-| |--------x----------x----|-| t i t i t i t i
The next step is to replace the strum with something - and what that next thing is depends on what you want to do. That's where the whole "style" thing starts to come together.
The tricky part here is that jump from the "boom chuck-a" to creating your own style doesn't happen overnight. In order to expand on that simple picking pattern you have to work with it until you "think" in that rhythm. This is kind of hard to do nowadays because guitar students - like modern "clawhammer" banjo students - are usually encouraged to copy arraignments of experienced players rather than learn the core skills of the instrument.
Anyway, the basic idea behind fingerstyle guitar is that you either have a monotonic bass: E+--------------+--------------+ B+--------------+--------------+ G+--------------+--------------+ D+--------------+--------------+ A+--------------+--------------+ E+--0--0--0--0--+--0--0--0--0--+ 1 2 3 4 1 2 3 4
or an alternating bass. E+-------------+--------------+ B+-------------+--------------+ G+-------------+--------------+ D+-------------+--------------+ A+-----0-----0-+-----0-----0--+ E+--0-----0----+--0-----0-----+ 1 2 3 4 1 2 3 4
You can use your thumb and two fingers or your thumb and your index finger. I'm a thumb an index finger picker myself- but I'll still throw my middle finger into the mix whenever I need it. in the long run it's not really that big of a deal because of the way the next step works.
See, in fingerstyle guitar there is only so many places to throw in a melody note.
It can be played at the same time as the low bass:
(alternating bass out of a C chord) E+--------------------+-------------------+ B+----1-------1-------+---1-------1-------+ G+--------------------+-------------------+ D+--------2-------2---+-------2-------2---+ A+----3-------3-------+---3-------3-------+ E+--------------------+-------------------+ 1 2 3 4 1 2 3 4
It can be played at the same time as the high bass:
(alternating bass out of a C chord) E+--------------------+-------------------+ B+--------1-------1---+-------1-------1---+ G+--------------------+-------------------+ D+--------2-------2---+-------2-------2---+ A+----3-------3-------+---3-------3-------+ E+--------------------+-------------------+ 1 2 3 4 1 2 3 4
It can be played before the low bass:
Between the high and low bass:
(alternating bass out of a C chord) E+----------------------------+---------------------------+ B+-------1------------1-------+------1------------1-------+ G+----------------------------+---------------------------+ D+-----------2------------2---+----------2------------2---+ A+---3-------------3----------+---3------------3----------+ E+----------------------------+---------------------------+ 1 2 & 3 4 & 1 2 & 3 4 &
Or between the low and the high bass;
(alternating bass out of a C chord) E+----------------------------+------------------------+ B+-----------1-----------1----+---------1-----------1--+ G+----------------------------+------------------------+ D+-------2-----------2--------+-------2---------2------+ A+---3-----------3------------+---3---------3----------+ E+----------------------------+------------------------+ 1 2 & 3 4 & 1 2 & 3 4 &
And if you mess around with those four places to stick in melody notes you wind you with a whole lot of cool stuff you can pull off.
Creating a melody line isn't hard if you can get a grip on holding a chord (so you have your bass notes) and blending the melody line into those four spots.
The easy way to work up to that is to take a bit of a scale and mix it into the alternating bass pattern.
What I usually start folks off with is strumming a a plan old C chord, then strumming the C chord and adding the pinky at the first string at the third fret to the chord form and then moving that pinky over to the second string at the third fret. If you mess around with that you can start getting the melody of Freight Train and a bunch of other tunes.
Agter they get used to moving stuff around in a chord for I'll have them hold a C chord and use the little finger- and index for that first fret note- to play this piece of the C scale E+---------0---1---+---3---1---0-------+ B+-1---3-----------+---------------3---+ G+-----------------+-------------------+ D+-----------------+-------------------+ A+-----------------+-------------------+ E+-----------------+-------------------+
Then add the alt bass: E+---------0---1---+---3---1---0-------+ B+-1---3-----------+---------------3---+ G+-----------------+-------------------+ D+---------2-------+-----------2-------+ A+-3---------------+---3---------------+ E+-----------------+-------------------+ 1 & 2 & 1 & 2 &
What you wind up with in this last example is what Doc Watson uses for just about everything, It's the same pattern Leo Kottke used for Fisherman, Merle Travis used it to death - in fact I don't think there is a way to count how many times this little lick has been twisted around by guitar players.
Once you can play it a written the next step is to play with the rhythm. Add in a brush, a hammer-on, a slide, a pull-off. Play around with the timing. Play around with the phrasing. Constantly screw around with it until you can start using to to express how you feel at the moment.
Play simply. Sing a couple of thousand folk songs and give yourself time and space to put it all together.