What's the most effective way to stay productive while working remotely?

Routine! Create and stick with a routine. Especially, at the start of your day.

Once day I read article on this topic. There were a lot of pieces of advice in it. And one of these has been helping me during last three years. The trick is very simple: you have to imitate usual office routine. Before starting workday you need to dressed in normal clothes and go outside and take a walk a bit (may be go around the house), and after that start your work day. At the end of the day, repeat in reverse order )