Song Writing Tips?

Listen to artists with the style you're going for. It'll help you figure out just how to structure everything.

You might want to think of a theme you are going for, too! It could be a love song, a sad song, something that fits you the most at the moment of writing!
You don't have to write a full song in a row also, you can start, for example, writing down random lyrics you have come up with or try to write the chorus part and then put everything together.
As for the music, you might want to start with something easy, like I'm playing guitar, I would just put together a few chords and then see how it sounds. Then I would start to think of a melody and then I would make the melody different for different parts of the song. Then I would add some cool effects to it.
Hope this helps!

bro just think about your life think about things that have made you happy sad confused etc try saying the things that you couldn't say before in your song

It's difficult to tell you how to come up with a melody, because that's something that usually just comes... For me anyway. But I suppose what I do is find a band or song, or more than one that has the sound i want to have, and I listen to them over and over for a couple days, and a melody of my own eventually surfaces. Either that or I'm playing my guitar, and something just comes up.
As for finding a new process, my process is usually where I write the song and the music together at the same time, and I can't finish the song if I don't have music. But that's just me.
'aneniine' suggested a good thing: Doing a theme. That always helps!
If you're a beginner song writer, you may want to start with shorter songs, and then gradually move forward to longer songs as you get better, so it's not so overwhelming.
I don't know much about harmony... I don't have a band, so I can't tell you that one. Sorry.
But anyway. I hope that some of this helped.