Write stuff! Everyone says that they can't get newhere writing music... and that they suck at it... but most people can do it if they just sit down... and play... and play.... and play and play and play! Try making up a riff and harmonize it... in 5ths, 3rds.... try learning the tricks on the site and using them in your playing! If all else fails, hum a melody that comes into your head and transfer it to guitar!
good luck man