The best advice I can give to people who are thinking about starting to invest in art is to start small. There's no such thing as a bad investment, but there are good and bad investments. When you're just starting out, it's easy to get excited about the prospect of making money and not think about the potential for loss.
The key is to always be rational and realistic—if you're not willing to lose everything you put into an investment, then don't put everything into it. I've seen a lot of people get into trouble because they invested too much or too soon. If you're just starting out and have only got a couple hundred dollars, don't buy anything more than that! You'll be able to try out different artists and styles without putting your whole nest egg on the line.
But if you're serious about investing in art, I'd recommend starting with something simple: prints by artists whose work appeals to you. If something speaks to you visually and emotionally, chances are it will speak to other people too.