Organise your inventory very well. This is extremely important.
Rename your notecards, objects, Landmarks, etc. so that they make sense to you.
Create folders and sub-folders. As an example:

Notecards folder

SL101 course notecards sub-folder

SL101 Lesson 1 sub-folder

• • • SL101 Lesson 1 note 1 overview
    • SL101 Lesson 1 note 2 instructions task 1
    • SL101 Lesson 1 note 3 language/vocab
    • SL101 Lesson 1 note 4 homework

Do the same with your educational tools, objects, landmarks, etc.

You could also create one folder for your course and then sub-folders for notecards, objects, textures, etc. instead of using the default folders that SL gives you.