I'd say that what's helped me the most is reading other artists' music. That way I've gotten a general feel for the way chord progressions are in most songs.
Don't try to write lyrics about something you don't understand. If you are absorbed by a feeling or really moved by something, then the words should come easier, because there'll be so much more to say.
I'd also say keep to a general structure: verse, chorus, verse, chorus, bridge, chorus. I mean, you can shake it up, but most songs follow that.
And most importantly, keep writing. I don't think anyone's songs are very good at first, but as you write more and more you'll get better.