Review papers at the publication level is very difficult to write. First off, you need to have a reasonable expertise on the subject that you're writing about. With that said, you'll also need to know 'all' the trials related to that topic. Of course you're going to have to weed out the ones that were performed poorly or had major limitations in the study, but it doesn't mean that you ignore them. In fact, with review papers, you'll have to address them as such.
Now when you write the paper, make sure you have a clear focus for the objective. Are you summarizing the disease state? the newest therapies? changes in the algorithm? or is it a personal opinion?
So depending on the type of research paper you're writing may determine the amount of background literature search you're going to have to do.
Another method to writing a good review paper is to see if there are any current review papers on the subject. If there are, look at their references and see if you can come up with those independently. If you are somewhat well versed in the topic, you should immediately identify the ones that are significant.
I hate writing review papers. It takes way too much time and isn't regarded as original research. But it's nice when you're not actively in pursuit of tenure and just want a promotion. But I know that promotions are not based solely on review papers, so original research is more of a priority than review papers.
My advice, if you're an academic, don't waste your time writing a review paper unless you know what you're talking about or if a journal 'requested' you write one. Spend it doing research. But if you're a student, well, start those literature searches.
Good luck.
