I want to start writing songs for the guitar. I usually just play covers for fun or learn scales, chords, arpeggios and licks to work on technique. I want to keep my focus on writing on an acoustic and then transposing it on an electric.

Anyone have some tips on how I can get started on writing songs? I really have no idea how to approach it.
Well this will probably be of no help, but ya never know. I started just by putting my fingers down in random positions, played and if it sounded good. I would try to find another chord or triad that followed it in sound and tone. If it sounds bad, move some fingers around a bit. Sooner or later your gonna find a nice chord. Also, I would recommend trying to write later at night. It has something to do with the chemicals and what not in your brain lol.

Thats how I started out and what I still use sometimes today and ive been writing for over 2 years now. It all started by me taking one finger off of a power chord.

Well, I hope that helped somewhat if any. Good luck!
Well that does help a bit. I want to try and start picking a key like C minor, find the scales chord progression and do something like that but I don't know which chord forms are best (I-IV-V; I-VI-IV, etc.) And when I start thinking about structure and following keys and all of that stuff my creativity shuts up and I just end of picking chords and when I lay down a chord progression, the melody or any single notes that I try to play over those chords never sound right; time wise or note wise.
I tend to avoid thinking about music theory at all when I write until I have at least a general idea of what I want it to sound like. Like Deathro said, I kinda just play around until I find something that sounds "right," you usually know it when you find it. Then you can make minor adjustments here and there to polish it up.
Yeah it does. Learn about musical theory.

People will tell you all sorts of crap about theory "shutting up your creativity" and "blah blah" ignore that.

Musical theory is like understanding grammar, it's not essential but it makes writing coherently a whole lot easier and faster. Instead of blindly guessing what will work. You can say..."What needs to happen in this next section, how do I join these two parts together? How do I modulate (change key) to create movement that highlights lyrically what I'm trying to say?

It gives you different tools that you can pick and choose what will work best with each songs.

Everybody's different in their approach, start experimenting with different points. Riff first, lyric first, melody first, chords first, verse first. Try and find what will work for you. There no right way.

Personal I write melody and lyric first 90% of the time. And I build chordal movement from there.

Also finish all of the songs. Even if it's just two verse and a hook. You're going to suck, don't worry about it. But finishing stuff is the fasted way to get good. You can look at and see what worked and what didn't and apply that to the next song.

If you want any help on music theory, song form etc. Feedback on stuff you're doing. I'd be happy to look at it. I'm not an expert but I'll help as much as I can.