I always begin writing a song on my acoustic guitar, mainly because I think it’s way easier to organize chord sequences, work out melody, a good rhythm and get a good song structure without over complicating matters. I also think that if a song sounds good just stripped down to the very basics, then it’s generally going to sound good in a band situation, and to add others instruments and maybe move it on to an electric guitar is way easier. So my first tip would be to get the song sounding good on an acoustic guitar whatever genre or style you play.
Think of any great song and I bet you could probably play a good version of it on an acoustic with the vocal line. Writing on an acoustic also forces you to play simple clean chords which again is a good foundation to build on, so work from the bottom up like building anything.
Now, the next thing may sound like a contradiction, but don’t necessarily think that less chords will make writing a song easier. Believe it or not I recently wrote a song with just 2 chords, (B & Cm) and it was possibly the most difficult song I’ve ever written. The main reason being that you have to add interest to the song in an alternative way to chord sound. This can be done by a change of rhythm, tempo or accentuation but it really is quite a challenge. A great thing to have a go at though.
I would suggest 3 or 4 chords is a much easier prospect for a beginner to work with. Of course you have to make sure the chords work well with each other. Yes you could try and be experimental and come up with some wacky chord sequences but I wouldn’t advise this as a beginner. Write something simple, maybe around a 3 chord structure such as G, Bm, D or G, C, D.
One trick with 3 chords is what’s called a ‘turnaround’, so the verse may consist of 3 chords played in a sequence of 4, for instance G, C, D, C (repeating the ‘C’ chord is the turnaround). You could then make the chorus just a two chord structure and play the chords in a slightly different so maybe strum a D, let it ring out, then a G.
One trick I love to use in my songwriting is adding a false bass note which completely changes the natural chord sound. An F# bass note with a D Chord is a nice example of this and is used in many songs. Neil Young is a great exponant of this technique and it can be heard in his classic song ‘Only Love Can Break Your Heart’.
So hopefully there are a few ideas there for you to introduce into your songwriting.