With a demanding day job, writer's block can feel particularly frustrating (i.e. "this is the only time I have to write today, and the creative juices just aren't flowing, dammit!"). That's when I turn to a pen-and-paper stream of consciousness exercise. I set a timer for some period of time (usually 10-15 minutes), pick up a notebook, and start writing. It could be random words, phrases, sentences, or story ideas. The point is that I'm writing and not judging what comes out. Sometimes, when looking back later, I'll find hidden gems that I can turn into stories. If I'm stumped on a particular story, I might switch it up from a truly free-form exercise to a slightly more focused one. Rather than bang my head against a wall thinking "how can I finish this story so I can move onto the next thing", I'll give myself some time to journal on my topic. Taking a step back can really help me figure out what I'd wanted to say in the first place.
Another more structured way I punch through writer's block related to a specific piece is the use of bullet points. Sometimes I find myself off on a tangent, and I need to guide myself back to the point. So I'll start making bullet points about my topic, which allows me to quickly see (1) what I think is important about it, (2) what I've already covered, (3) what I still need to discuss, and (4) where I need to trim from what I've already written.