How should I deal with bark chips in my garden?

Last year, I put down a plastic liner and covered it with bark chips to clean up the look of my garden and help prevent weed growth. Now it's full of gr clippings and debris (leaves, old plant growth, etc.) from the past year. How do I clean it out? Do I just need to lay new bark over the top? How can I prevent having to do this again in the future?