write about what you know. Life experience is always more apprieciated than the existential stuff. (I may have misspelled that...but you know what I mean.) Songs are all little stories and they should be believable. Write about your life. All forms of art are in some way a reflection of the human condition. But don't whine about your life...Everclear already has that genre beat to death.

also, repetition is a big help. Something cool to punctuate your main idea. Not all lyrics need to rhyme. Drama sells. Keep it simple. Listen to the beatles!!!!
When I can't think of a followup verse I look around myself and ideas flow in. If you get writers block, don't try to write in a couple of weeks and then the songs will come to you. I had to wait for about 3 months but I probably didn't need that much time. I just got lazy.