Science and pseudoscience, what’s the difference? It’s not a trick question, as you approach the cutting edge of science, where the known becomes the unknown and theories become wild and speculative the line between the two can be quite fuzzy. String Theory anyone? But in general the difference lies in that where science starts with facts and observations and arrives at conclusions pseudoscience starts with a conclusion and twists fact and observation to fit. The two most common avenues to pseudoscience appear to me to be: First, when a hypothesis is retained long after dis-confirming evidence should have rendered it obsolete. Adherents of the “Vaccines cause Autism” movement would fall into this category. Second would be those who attempt to prove their own pet ideology by either conducting flawed research or by willfully misinterpreting the work of others. Creationists and Intelligent Design proponents might fall into this category.
Correctly discerning pseudoscience can be difficult, especially if it appeals to our own biases. Some things to consider are: Arguments from authority, real science shouldn’t be decided by a chosen few, rather it is the sum total of a multitude of efforts and advancements are evaluated by the scientific community as a whole and finally a consensus is reached. Insufficiently detailed references to supporting data, it is important to be able to find the primary sources that are being used to support a position so that you can read it yourself and determine if it has been correctly interpreted. Reliance on testimony, look at the quality of the references used, if they come mainly from personal experience they may not be reliable.
Finally, you may want to look at a larger sampling of the scientific community and see what they have to say about the topic or person you are interested in. There are bound to be many sides to the issue but you may pick up on the general flavour of scientific opinion. Good luck and happy investigations.