Hello, and welcome back. Yes, it's angryskykitten with his second lesson for, and I must stress this, beginners.
One
This is done before the style is chosen, the theme is chosen, the music is written or anything. Frame of mind is key. Don't be dejected sitting there thinking 'My God, this is crap, they sound awful, I'm no good at this... '. Be positive, but not big-headed.
Now then, you want to pen lyrics right away. Don't force it. That is rule one: forcing is not your friend. If you have writers block, fine. Go off for five minutes; make a cup of tea or something, then go back to it fresh.
Two
Some people say 'You always have the music done first, then you can write real lyrics on top'. That is nonsense. There is no 'always'. It's personal preference. You can do it either way around. Sometimes it's obvious what kind of lyrics a rhythm line needs; sometimes you've composed something then you come across some lyrics you've written days before and (maybe with a little tweaking) they fit perfectly!
Three
On to the actually lyrics. They don't have to make sense. They don't need any clear meaning or underlying theme. Just write whatever you want about whatever you want. Meaningless lyrics don't stop Red Hot Chilli Peppers, for example. Weird lyrics didn't stop System Of A Down and so on.
If you do have a theme you want to write about, think a little about it. Is it something you feel strongly about? You can take random things in your life that have happened to you, or you've heard happen to someone, with relation to you theme and just throw that in. Doesn't even have to rhyme. Many a great song is spoiled lyrically because the lyricist tried to rhyme.
Surprisingly, some of the finest lyrics can come from the most obscure things. Lucy in the Sky with Diamonds was based on a picture one of the band members' son drew. The song simply described the picture.
The Scorpions song 'Wind Of Change' begins with 'I followed the Moskva/ Down to Gorky Park' and is about following a river to a theme park in Russia.
Some of the most ridiculous metaphors or phrases can make some of the finest lyrics.
Four
Arranging the lyrics. Depends on the kind of song you want it to be part of really. Verse, Chorus, Verse, Chorus (a popular choice), or the same musical structure, just without repeated chorus (so the same rhythm line, just different lyrics each time), or whatever. Experiment. You never know what you might come up with.
Five
Don't spend all your time trying to fill every last beat with words. Leaving unexpected gaps or holding notes over a few beats instead of singing more words can make a piece far more interesting.
Six
Oh yes, and you're your own worst critic. What you write and think is pants, someone else could come along, look at it and think 'Wow! ' Just mess around really and don't let it get you down if someone goes up to you and says 'These lyrics are rubbish'. For one thing they could be wrong. Saying that though...
Seven
Take constructive criticism. Someone who comes up to you and says 'These lyrics are crap! The worst ever! ' is just being stupid. Someone who says 'This doesn't sound too good' or 'It doesn't really fit with the music': listen to them, take your lyrics away and change them a little, or start again. But...
Eight
If you don't have any confidence in what you're doing, there isn't really a point. Don't be put off. Ever. Just have fun writing them, otherwise, what is the point?
I cannot teach you how to sing these lyrics, that is entirely up to you, but sometimes singing lyrics in the right way can save a bad line or two.
Failing that, so many people don't listen to the actual lyrics: you can get away with so much if you just pretend you know what you're talking about.
Disclaimer
A lot of this may seem obvious, but you'll be amazed at how many people miss the obvious out completely.
Regards to my mate Chuck, who proof read this thing for me. Thanks mate!
/ my profile 
Glad to be of help people.