Beginner organists usually struggle with reading three staves of organ scores.
Although they may have some experience in reading piano scores with two lines, adding just one more line for the pedals seems to be a daunting task.
Not only do they lack the technical ability to play the right notes on the pedal board, but also they have to face another challenge - their left hand naturally wants to play the bottom line.
The prospective organists might get frustrated with these difficulties and quit practicing the organ.
However, there is an easier way to read three lines of organ music which will help you to simplify this task.

1. Practice 1 line at a time first.
   Since 3 stave notation is new to beginner organists, it is not surprising why they find it so difficult to read all the lines together at first.
   However, we should remember that even two lines of piano scores were difficult to read at first.
   Therefore, I suggest you practice one line at a time in the beginning.
   For example, when you take a new organ composition, don't attempt to play the entire organ score with pedals, but practice the right hand part at first, then play the left hand part, and, finally, master the pedal part.
   This will be the hardest task.
   
2. Practice 2 lines later.
   When you can play your solo parts at least three times in a row correctly without hesitations and interruptions, put 2 lines together and practice them.
   You can work in the following dispositions: the right hand and the left hand, the right hand and pedal part, and the left hand and the pedal part.
   As in the previous step, try to achieve some fluency and play each disposition without mistakes, with the right articulation at least 3 times in a row correctly.
   The most difficult disposition undoubtedly will be the left hand and pedal part.
   Here you will have to repeat the most times.
   Stop at each measure when you make a mistake, go back a few measures and correct each mistake.
   
3. Finally, practice 3 lines.
   If you are honest and practice sincerely the two previous steps this final step will not be as hard as it have seemed to you originally.
   Now you are ready to play all parts together.
   Again, work in smaller fragments for best results and correct your mistakes.
   

Note that every step requires practicing in a slow and comfortable tempo.
Although the concert tempo might be much faster, don't worry about it at first.
You will be able to play up to tempo naturally when you are ready.