START AT THE END.
You need to know what the ending of a plotline is, At least the final gut punch you plan for the reader to have. You can have an epilogue afterward, but you need that final scene in your head at least. Just writing because "I have a cool idea." Doesn't work. You need to know the ending.
Most books are three acts.
You need a plot that starts then finishes in Act/Act, in order of importance:
1/3
1/1
3/3
2/2
1/2
2/3
What I mean is you introduce a plot in Act 1, then it ends in Act 3, followed by Act 1 ends in Act 1.
The overall plot, that goes from plot 1 to plot 3 is the most important, but 1/1 is the second most important because it KEEPS THE READER READING.
That means, before you start the story, you need to have 6 endings. I don't care how much you write it out, but you need 6 plots and 6 plot endings. ANYTHING ELSE IS BOTH UNNEEDED AND DANGEROUS. You also need to know how the plot STARTS. So you need 6 beginnings and 6 endings. However, if you work those out ahead of time, everything else is just filler to get the story to move from one key scene to the next.
For example:
1/3: Joe is summoned and he has to defeat the demon lord
1/1: Joe is dropped into a strange situation and needs to adjust.
3/3: Joe will have a setback he needs to overcome
2/2: Joe will go on a training montage.
1/2: Joe will encounter the miniboss and have to overcome them.
2/3: Joe will have a romance subplot where he meets a girl and they fall in love by the end.
So three things begin in the first act, 2 starts in the second, 1 in the last.
There is one conclusion in the first, 2 in the second, then 3 in the ending
(and if you do it well, it all comes together in one scene.)
It's simple, it's formulaic, IT WORKS.
If you do this, you won't "write in the wrong direction" because you know where the ending is. Once you work out those 6 starts and 6 ends, everything else in the book is just connective tissue.
I find once the Big set pieces are done, it's fairly easy to just sit down and write the connective tissue.