Create a Folder in the LTSpice folder called 'MyWork' [ or a name of your choice], which will be YOUR working folder.
Inside the MyWork folder, create folders for the various projects that you are working on OR for the Types of IC being used.
eg: I have 'MyWork/OPA and MyWork/555 etc, in that way I can quickly find projects I worked on earlier.
NOTE: .asc , .asy , .mod are File Type Folders that LTS uses.
When you import files place the asy files in the C:\Program Files\LTC\LTspiceIV\lib\sym folder.
Place the .mod , .lib in the C:\Program Files\LTC\LTspiceIV\lib\sub folder.
Place the .asc files in the appropriate folder under your MyWork folder.
eg: your LM324.asc could be placed in the C:\Program Files\LTC\LTspiceIV\MyWork\OPA folder.
Its important that the .include LM324NS.mod text is entered as a Spice directive on your circuit, when using the LM324NS model.