This is something that everyone endures at some time in their writing careers. It can happen often for some, while some may not suffer for long periods of time. I'm talking about the dreaded 'writer's block', and yes it has even afflicted yours truly!
In my experience, there are many ways to mitigate this small problem, and I say small as it really is a minor issue but if left untreated will grow, so nip it in the bud!
The first thing to do is to admit that it can and does happen and will affect ones writing life.
Secondly, to avoid the block, pick an exciting topic - one that you are passionate about and have some kind of expertise/experience with. An example would be like the piece I wrote in my blog about Chilli chicken pieces. I love chilli, and I wrote about the product, how I cooked it, and what it tasted like. I could also talk about chilli heat and its measurement and could have gone into depth about the biochemistry and physiology but tailored my article appropriately.
The third way to prevent the block would be to research the topic in detail. Read books, newspapers, other blogs, talk to people in the field you are studying in person or email or by phone. When all the information is gathered, then sift through and summarise and put into a plan. Then start to pad it out.
The next way to reduce the block is to have a dedicated time slot to write and a writing station. I like to do my writing on a Friday, and I would usually do so in my living room while watching a movie. Others may wish to do so with a glass of wine or in their study etc. Sometimes a change of scenery is required, and I would often take myself off to a coffee shop or the library, even on the job.
In summary, admit that a writer's block may happen, have a plan and stick to it, research it thoroughly, and if there is a block, then try a different approach. Happy writing!