@browncoat - It's good advice to follow. I know for many people who are starting out, particularly creative people who just want to sell a few paintings, or whatever, the accounting side of things seems quite overwhelming.
But it's really not that complicated. And, if you are worried about it, there is plenty of information to be found in the library or online. I think good examples of accounting policies can be found all over the place, actually, so you have no excuse for not sorting this out.
Even if you have already started, it's never too late to change your accounting method.