I've changed the way I write recently which has helped a lot. I used to just pick up an acoustic and jam around until something I stumbled onto something I thought sounded cool but I found it a pain to do and it put me off writing cos anything good more came by fluke.
Since I started Uni tho I've had to adapt to being able to write the basics of a song as quickly as possible but I've found a more comfortable way of doing things which is to settle on a sound that you want find 2-3 songs that you want it to sound like and cross reference everything from them so bringing up guitar charts and listening to them over and over for similarities to use as a pastiche. Which can sometimes come across as stealing but when you notice the amount of similarities in songs who cares haha I asked Youth from Killing Joke if he was annoyed about Nivarna stealing the riff to eighties and using it in come as you are and he said "well we stole that in the first place" which I liked.
I've started carrying a note book with me everywhere and my phones audio memo is littered with melodies that I was worried I'd forget.
Granted I write with an extremely pop styling and try to keep things as simple as possible for that reason such as using as few chords as possible...Apart from one song that has 25 but that doesn't count
oh and I always have to have a title first which drives me crazy!