Good question. Solid research is something I learnt to do whilst studying for a teaching degree and it's absolutely necessary if you're intent on writing an article you know nothing about.
I gather information from four main sources : the internet, newspapers/magazines/journals, t.v. and books.
I make sure I have a notebook at hand and take copious notes, depending on the subject matter. For example, I recently wanted to write about altruism and the care certain animals display when helping family members or others.
All I had to go on was a video I came across on youtube which kind of got to me.
I watched a BBC documentary on a similar subject a few days later and took notes - basic facts and names - which I later looked up on line. I got some juicy material. The local library was also helpful so I took more notes in the reference section and ended up with about 4/5 pages covering 10 animals.
Wikimedia commons has some useful images in the public domain, I used those and found them helpful for when it came to describing the anatomy of an animal.
Research can be time consuming for subjects you know nothing about - how much time do you want to spend making notes and how many words do you want in your finished piece? Will it be worthwhile? Big questions, especially if you're writing to make money!!
It's about getting a balance between accuracy, writing style and time but I quite enjoy the challenge and it keeps the brain ticking over, don't you think?
Where necessary I attribute the source.