Hello folks!

I've hit a complete block here.

I'm trying to get my head around to start writing a song. Thing is. I find it REALLY hard to begin. I want to write in an open tuning, but I don't know which one I should choose. I'm planning to do "coffee shop" style of music. Mellow music, acoustic based. Could I get some advice? Which tunings would suit it? I'm currently in Open G, but I'm thinking it's too bluesy?

I wouldn't really worry about the tuning too much. It's more about how you're using the actual notes. Generally you want to write in whatever tuning your guitar is normally in though. If you're performing to a crowd then no one wants to sit around while you change tuning between every song. Personally I'd say stick in standard tuning unless you have a specific reason to use an alternative tuning.

As for beginning a song, either lyrically or musically, you need to conjure your own ideas to start from. Writing a song with nothing specifically in mind is almost guaranteed to just give you a bad song. You shouldn't really just start writing songs for the sake of it unless you're doing it professionally and need to meet a deadline.
like that guy said tuning is pretty irrelevant and if what you are writing in open G sounds too bluesy then if you play it open C its still gonna be bluesy just a different key. My most succesful song writing comes when i have something i wanna start from. Like say i learn a strange chord or there is a certain interval i love ill just build off that, play what you hear in your head.

Also I find that writing is easier when you dont sit down and beat yourself up over trying to make a masterpiece, sometimes it just happens.