One other songwriting tip I have is to keep a notebook for writing words in. If you normally write riffs well and have trouble coming up with lyrics start by writing down words that amuse you. Words that rhyme. Interesting headlines from a newspaper. Sometimes you might write a verse or a song. Keep everything you write. Sometimes you will hear people talking as you walk by. If by chance someone says something interesting write it down (it can always be used out of context or could influence a song). I have a big stack of notebooks full of 1 liners, words, ideas, and songs. It's something to go to when you are having problems with inspiration. This is a great way to fine tune your lyric writing. Cut and paste lyrics have been used by many good musicians. It doesn't always have to make sense on the surface. If it has catchy words that sound good together, people will try to interpret it. It might make you look like a verbal genius!