Look for fresh topics to write lyrics about. Country songwriting no longer focuses on the tear-in-my-beer approach to writing. That doesn't mean you can't write sad songs or songs about hometown America and blue-collar workers. Those topics are country staples, and if you have a good set of lyrics and music for a song that fits that subject matter, write it down---but expand your horizons. Jot down ideas for lyrics that touch on social and political issues. The country music industry today allows you to take on any subject matter you can write a good song about.
Try stepping outside the traditional realm of country music, and blend pop sounds with the music you write. Think contemporary. Kid Rock and Jewel have had success in the country field, and Alan Jackson and Toby Keith have managed to crack the pop charts. There are different ways you can do this. Write songs that are meant for two singers, one from each genre. Try writing songs that use more than major and minor chords or traditional verse/chorus structure. If you get a chance, co-write a song with someone who writes in another musical genre than yours. A crossover hit can bring in huge royalties.
Respect the genre you're writing in. A lot of songwriters cross over without having any respect for country music or its traditions. They just see it as an easy way to write songs and make money. Regardless of the wide subject matter, country music is still primarily an American tradition that has its roots in hometown pride, working hard and being patriotic---and these values are taken serious in the country music industry. Country music fans can spot a fake who's in it just for the money, so write honestly and from a respectful standpoint.