What are some good starting points to begin writing songs for someone who possesses limited theory knowledge and playing experience (beginner)?
What are the essentials skills and knowledge for creating your own music?
Your question is very vague, but I'll try to answer it to you anyway.
You are actually pointing at three different skills:
I'll explain to you what these skills are and how to learn them.
Have you ever seen a dude with a guitar playing love-songs in a corner surrounded by pretty girls? Yeah, that's a good example for songwriting.
You don't really focus on what's being played, but on the "front" of the music. That's the melody of the vocals, the chords being played and the lyrics. This skill can easily be learned by picking up an instrument, finding a fitting progression and writing text that goes easily with the melody.
Just write poems with repeating patterns and do it a lot, that's the best way to improve. Keep in mind that songs aren't more than a poem, but with a melody.
A composition is the technical part of a song. What harmonies are being used? What arrangement of instruments do I need? What part is played by which instrument?
Compositions are covering the instruments of a song, no vocals or lyrics are needed here. If you want to make good compositions, pick up your instrument and write down ideas in a tablature software, such as Guitar Pro, Tux Guitar, Finale...
Get to know your instruments, write down musical ideas and work on them. Did you write a pop song and you're having an idea for a saxophone solo? Write it down. Did you write a classical interlude with violins and want to make it more powerful with a bassline? Write it down.
Write everything down that comes into your mind and do experiments. This will train your skill to understand music sheets, melodies, and how different tones work together. You might even find melodies you'd never think of when only playing your instrument.
While Songwriting is the front of a song and the composition builds up something in the middle, music theory is the backbone of anything you'll ever write. I'm not only talking about music theory, but everything you've ever experienced in music.
The songs you listen to, the techniques you've learnt, the theory you read... Everything builds up your musical knowledge. If you've been in touch with music at young age and already know how to play an instrument it's easier to know what music is.
If you've never picked up an instrument or if you weren't raised in a musical family, I suggest you to listen to as much music as you possibly can. Listen to whole albums (Dark Side Of The Moon by Pink Floyd is always my first suggestion when it comes to whole albums) and analyze the songs. What were the ideas of the musicians when they wrote these songs? What patterns are they using? What's the melody like? Listen to every single instrument.
It is equally important to develop knowledge with music theory. Best thing to do is to take music lessons (with an instrument) or to read a lot in music theory books.
Simple Tips For Making Own Songs
Here are my personal tips for anyone who wants to make his own music.
I hope this answer helps you and other rookies to get started, good luck!
How to begin writing songs? In my experience, generating songs without an instrument in hand can drive your acquisition of musical knowledge, and can drive and inspire you to improve your skills on whatever instruments you play.
For a time I worked as a lawyer's clerk, and walked all over town. While walking, I would compose songs, of course with no instrument - a capella. I could go over and over the new melodies, change them to make them more interesting without my playing skills (or lack thereof) as a limiting factor.
When I got home with this song humming in my head, I would be challenged to harmonize and accompany it, whether on guitar or piano, and so my skills increased by necessity. This challenge also led me to pick up some theory books and so moved me to expand my knowledge of chords, scales and progressions by both reading the text and working on the exercises. (There was a music theory book put out by the Harvard Press that was particularly helpful. I am sorry I cannot locate it online.)
So consider a different approach - start from the way songs express your relationship to your world, and let the songs that come to you drive your acquisition of knowledge and skill, instead of the other way around. Of course, this is not the only way to address your question, but you could certainly start from where you are, today, using an approach like this.
Understand chord progressions starting with I IV V from a blues song. You must know tension and resolution. In the blues progression it is easy to hear it. Then listen or get sheet music of songs you like and look at the chord progressions. The chords setup a template to put a melody over it. The challenge is the melody since many writers use common chord progressions.
Increase you vocabulary with many different styles and songs and analyze them. The analysis will lead you to expressing yourself more accurately. This will take time and patience but is worth it.
One thing you should understand is the relative minor theory. It will be much easier to write songs when you know this. You can create good music with a few major chords and their relative minor chords mixed in.
I have been playing and writing music for 10 years, and not until recently have I started studying music theory. That concept really opened up some great ideas for songwriting.
These are all very good answers. For a more in-depth dig into the issue, I recommend "Tunesmith: Inside the Art of Songwriting" by Jimmy Web, who was a highly successful professional pop music songwriter. "Tunesmith" gives you the music theory that is essential for songwriting and actually takes you through the process of composing a pop song.
Jimmy's info is a little dated as his biggest hit was "Wichita Lineman" but most of the information is universal.