I can tell you how I write but I don't know if it'll be much use to you... everyone does it differently.. although I know my two band mates usually write in a similar way to me...
I'll begin by picking up my
acoustic guitar and start strumming some chords...
{quite regularly the songwriting process stalls here... I put down the guitar and forget about it for rest of the day...}
sometimes, however, a new chord shape or something will kick start something fresh... or i'll try a different tuning and find something inspiring (since I don't know the chords I am forced to invent them)...
{another potential stalling point - often guitar chord/riffs/progressions never come to much}
from there I start to sing nonsense words to the beginnings of a melody... sometimes a chord chosen will dictate where the melody goes.. or sometimes I need to search through chords to find the one that the melody is asking for...
the nonsense words carry meaning - there is usually an emotion or a feeling underneath that needs to come to the surface... at this point you need to feel the music... you also need to be alone cos you are sound like a babbling idiot as you let try to let the words bubble to the surface and mold themselves into something resembling english... this is the funny part... I think my subconscious mind knows the words it wants and is feeling the emotions connected with them while my conscious mind is still in the dark... it's important here not to rush lyrics... you just need to keep babbling/singing and they'll bubble up eventually...
once I have a verse (and probably a chorus as well)... that's when I take a step back and ask myself... Ok what is this song about? Who is singing? (it's not always me) Why is he/she saying the things he is? By asking myself these kinds of questions I have a better idea of what to write to plug the gaps that the babbling/bubbling process didn't create... often these lyrics are just what I call padding... they fit around what I came up with previously without changing the meaning of the song too much...
at this stage the song is half completed... it likely still needs more instruments playing and properly arranged into a song structure...
if the other two guys in the band are around we'll probably jam the song and I'll sing it as many times as they like while they might write a bassline, or a mandola part, or an electric guitar part etc...
or if nobody else is about then I'll record my self in cubase and start to layer other instruments over me and the acoustic...
after that the last thing to do is to chop slice, copy and paste... drag around etc... to get the perfect song arrangement...
That's the song written... then you've got to record it properly... still trying to work out how to do that!