I really like the responses above! Especially, norcal68's. Don't stress and just let it flow. Practice.

Write from your heart. Start with writing about a subject or someone that you love, or a subject about which you have really strong feelings. It makes it easier to write if you have some inspiration. Already being emotionally involved with a subject or person can help to get the writing juices flowing.

Rhyming is important, but not an absolute, as is short sentences (also not an absolue) that make sense to some kind of rhythm. Doesn't have to be perfect at first. Revisions can always take place later.

Here, I'm going to make up a possible song right now. For real. I'm going to call it "I'm in Love with You."

I'm in love with you
Do you love me too?
I could be blue
If you don't love me too

Take me in your arms
Surround me with your love
Hold me and mold me
I am yours

I love you today
I love you tomorrow
I love you always
Always and everyday

We can play games
And, I love you so
But, my love feels the same
As I want you to grow

And know, know, know
How much I love you!

Okay, I know, totally hoaky and not really inspired. Rhymings off a bit, too. Needs a lot of revision and maybe starting it all over again from scratch. But, there is some substance there from which to evolve it into a song that might be usable and enjoyable by others.

The important point is, that I just stuck my neck out and did it. You could too!

It took me maybe a total of two minutes to write that.

I just wanted to show you how to just start doing it. Doesn't have to be perfect. Takes a lot of practice and review from others to see if it is something that other people would like to read or hear.