Another writer's block tactic for me is to review the very extensive characterizations I write for the protagonist, antagonist, and supporting characters of my stories. Quite often plot points, both major and minor, come out of these characterizations, as well as traits and odd tid-bits that make the characters more interesting and quirky, and act the way they do throughout the story. These traits can spur a new (and often exciting) direction for them and the story.
I've been a member of several writing critique groups for several years and it never fails to surprise me how many new writers don't spend the time getting to know their characters by writing comprehensive characterizations before they start writing! They need to do the work! Most have a story structure or outline they follow, but the "bones" are not enough. The "flesh" of the story comes from the characters' actions/reactions to what happens in the story, as well as the character of their natures that act as a stimulant/catalyst for what happens. - The White Rose
I don't think I can underestimate how important characterization is to your writing. No matter what the story is you are telling, it is filtered through the characters who are experiencing it. And often, when we get stuck somewhere in a story, it's because the character is doing something that isn't right for them.
Each character has to have something they want and something they need. These should not be the same thing. Conflict, which is so crucial to a story, arises when what the character wants is different to what she needs. And when one character's wants and needs oppose another character's. As each character fights through the story to get what they want, other characters will get in their way because they too are fighting for what they want. These wants and needs should be set up early in the book as these are what compel the characters to move through the story, interact and finally resolve whatever the central conflict might be.
Every decision your characters make will come from these wants and needs and the more in opposition they are, the more tension you will create.
While I don't think it's entirely necessary to write long, detailed biographies of each character before you start writing (but hey, I'm not an outliner either so do whatever works for you), I do think it's absolutely critical you know your characters well. Even if you never put any of it on the page, your characters need to have a past that has informed who they are at the time the story takes place, a set of beliefs that define them. This will drive the ways in which they react to the different plot elements you put in place to thwart them.
When you find yourself stuck at any point, go back to the last place your characters had to make a major decision or action and check that the way they responded fits with the personality and backstory you have created for that character. Does it go against their moral code? Is it beyond the physical capabilities you have outlined for that character? While people do extraordinary things, particularly in times of distress, how they respond is almost always in line with their personalities and one of the fastest ways to break your story is for your character to do something that isn't.
Hope this was helpful!