Alrighty. Songwriting/lyric writing. It's tough at times, and takes a lot of natural talent to do well. So I kinda wanna help with this compilation of what I do.
1. Most Lyrics These Days Suck
Do not worry about writing amazing lyrics as you start. Unless you're playing acoustic songs with just a guitar in the background, the music will generally be more important, so don't really stress out about it. Most individuals here play some offshoot of rock or metal, so the guitar is going to be more prominent than the voice. Look at the Beatles. They were original, but if you look at their lyrics, they are fairly bad, but they still are perhaps the most influential band in the evolution of modern rock. Same thing with Metallica. So just chill out, listen to some Queens of the Stone Age, and realize that your lyrics aren't that bad, and just write. You can fix them as you evolve as a writer.
2.1 Try Singing Over Songs
This is kind of a duh, but regardless, I found it helps a lot. I'm not saying freestyle rap over Eminem or something, but if you're driving along listening to a song you really like, just ignore the vocalist and make up your own words. Chances are, what you write at first will be clich but it will get your mind working faster to devise rhymes and form coherent lyrical ideas. As you go along you'll go faster, and this will also help massively with developing your ability to make up vocal melodies.
2.2 Try Singing Along To Songs
Also a duh, but by doing this you find certain word combinations you like, and can also work on hitting harmony parts if you're not doing lead vocals or just want to shake it up.
3. Don't Be Afraid To Borrow Concepts
Everything you have ever thought has been thought before, and thus if you like something, it's been done. So don't worry about being overly careful with avoiding any conceptual quotation. For example, although I didn't realize it as I wrote the song, I alluded to two song titles in one of my bands songs, simply because they fit the theme.
That being said, don't borrow too much. I read lyrics once in which the writer had borrowed two whole lines from Manson and didn't realize it. If you really like a pair of lines or more, make sure you got it from inside, or paraphrase it somehow.
4. Write What You Know/change Themes When You Write
This has been very difficult for me personally, so I feel like a hypocrite, but nonetheless, I will say it. I am very introspective and principled and thus when I write, I feel the need to put those principles and philosophies into effect. This is something every songwriter should do, so they can truly relate to a song. However, one has to be careful not to always write about the same thing. Rage Against the Machine is a perfect example of a band that does this. Their lyrics are very predominantly anti-establishment, and although they're good and fun to listen to at times, they become a bit dull at times. Spread out what you try to say, but don't sell out and not say what it is you want to say. It's a difficult balance to find that takes a lot of thought.
5. Try To Avoid Writing Music To Lyrics
It is easier to write lyrics to music than vice versa for one simple reason: the voice is easier to jam with by feel. So have the instruments in your group make something up, and then make lyrics to that. It is easier to match the sentence length and structure and melodies to music if you actually have it. Vice versa, you might be forced into a situation where you simply can't sing the way you want, or will have trouble changing the lyrics later.
Given the way my band writes songs, I've found the best way is to just relax and write a few lyrics that have different feels (heavy, emotional, driving, etc) and keep them handy, then when you guys are writing a song, try them out until one fit's to it, and make small adjustments to the music to perfect the fit.
6. Vocalist: Pick Up Another Instrument
If you're just a vocalist, learn another instrument, something your band doesn't really need. I know the tambourine thing is a joke, but you can really add to a song by adding say, a violin, or a keyboard while you're not singing.
7. Allow People To Play Alone
This applies mostly to guitarists, but also any vocalist who likes Avenged Sevenfold or similar bands. Shut up for once. Allow the drums to do something, or the bass. I realized how important this was just yesterday when we were writing a new song, and we had decided to cut out the guitar for two measures and just have the drums doing a beat, and literally 8 times in a row the guitarist kept playing. Chill out and let the rest of the band do something.
There is more stuff that is just purely personal taste and can't really be adapted if you don't agree, so I'm not going to bother with it.