In all honesty, I think one of the biggest difficulties when it comes to citations is people often don't know what their source actually is. Journal articles and books are easy to cite; they have standard components and there are many models to use as examples. Information that you find on the internet and anything that isn't a standard source can become tricky. If you are tempted to cite a source as a web site, double check and make sure you don't actually have an agency report, a white paper, or something else that doesn't fit into a neatly defined category.
Remember, if you put time and effort into creating citations at the beginning while you're researching, dealing with them as you're writing will be so much easier. Also, if you're using the write-and-cite functionality of citation management software, you will be in great shape.
For help with citations, please feel free to contact me or any librarian. The Purdue OWL, of course, is a favorite resource. We also have the printed APA Publication Manual and can look up information for you from that book.