I'd also say learn songs you like (that sounds obvious!) by bands you like. When I was learning I was a big Rush fan (still am!), so I bought their 2 volume songbook and learned the chords to the songs I liked and played along. When I began to write my own songs, they sort of followed the types of progressions that Alex Lifeson would play, and of course, my songwriting got better the more guitarists/bands I 'incorporated' into my playing. I'm also self taught, and back in the 80s there weren't no internets tubes to download tabs and such, so when I was learning chords I would just make stuff up to practice changing from one to the other, so I kind of taught myself by writing pseudo-songs as chord practice.
Lennon/McCartney began writing songs trying to copy Buddy Holly, so a lot of their very old material has something of that sound, but of course, they moved on.
I also tell everyone that mentions they're learning to play the guitar to order The Guitar Handbook by Ralph Denyer. It's awesome. It goes into everything from how guitars are constructed, to brief essays on great guitarists, intro to music theory, playing different styles, alternate tunings, modulation...the works.
http://ec1.images-amazon.com/images/P/0679742751.01._BO2,204,203,200_PIlitb-dp-500-arrow,TopRight,32,-59_AA240_SH20_SCLZZZZZZZ_.jpghttp://www.amazon.com/-Guitar-Handbook/dp/0679742751/sr=8-1/qid=1157179560/ref=pd_bbs_1/103-5269415-6449457?ie=UTF8&s=books(edited to add more stuff..!)