Get my phone out of sight, disable access to websites that distract me, put on some music with no lyrics and low musical movement (often OSTs for movies or games). I also have a separate fun and work computer which helps it be a distinct environment.
More abstract, I got rid of social media and started reading again in order to increase my attention span. "Feed" style sites decimated my ability to concentrate.
Soundtracks definitely. Jazz too although I find using vinyl for this too distracting. I generally fire up a streaming service or an old 5 cd carousel player full of CDs. I also get grumpy during work that requires extended concentration which helps a lot as the long suffering family knows not to interrupt :-)
More abstract, I got rid of social media and started reading again in order to increase my attention span. "Feed" style sites decimated my ability to concentrate.