Theory-Of-Xerosis
Experiment and just see what happens. Learn how to do fingerpicking to make those chords sound a bit more interesting with more going on. Or try adding hammer ons, pull offs, and slides between chord changes to add a bit of spice. But the main thing is to just play around until you find something that is different but sounds good. Experiment and open your mind to the strange.
^What they said.
And
listen to the style of music you want to write.
Why is that so big and obnoxious? It is THE most important thing for any musician/composer/dabbler to do. All of my (serious) jazz friends transcribe solo lines by their favorite players. This gives you a look at what the player's doing, how they're coming with it (when you look at the lead sheet), and what kinds of things are common in the genre. But seeing as how not everyone in the world can transcribe (~raises hand~) just listening is fine. You get the style in your ear, mind, and body. And not just jazz (that's just the class I'm taking, right now).
I listen to a plethora of styles. The ones I listen to most, because I like them best, I can hear influences between bands, references to other bands (past and present), I know what kinds of things the different parts are going to be doing, and I can sing back nearly every line in a song I particularly like. Heck, I can come up with harmonies that fit that particular band for that style of song (up/downbeat). Ok, that last part's because I've sung alto all my life and have wanted to teach music for about the last half.
You don't have to be a trained musician to hear layers in the music. All you have to do is look for them.
And remember: it's called
referencing, not "plagiarism". Unless you write more than five successive notes.
(NOTE: the sarcasm)
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