From Greg Bennett running Linux Mint 17.1 (Rebecca) 64bit
and 
CL-USER> (asdf:asdf-version)
"3.1.5"
CL-USER> (lisp-implementation-version)
"Version 1.11-r16635  (LinuxX8664)"
CL-USER> (lisp-implementation-type)
"Clozure Common Lisp"

I am evidently missing a significant aspect of the way asdf looks for .asd files,
and will appreciate pointers to the appropriate information.


I have used quicklisp to install mcclim, and am trying to run its examples from the file  clim-examples.asd,
which is in ~/quicklisp/dists/quicklisp/software/mcclim-20161208-git/Examples/clim-examples.asd

Trying to follow Section 4.1 of the asdf manual:

The current contents of ~/.config/common-lisp/source-registry.conf.d/this-path.conf is
(:tree "/home/gwbennett/quicklisp/dists/quicklisp/software/mcclim-20161208-git/Examples/")

There is no file ~/.config/common-lisp/source-registry.conf

(probe-file "/home/gwbennett/quicklisp/dists/quicklisp/software/mcclim-20161208-git/Examples/clim-examples.asd")
returns
#P"/home/gwbennett/quicklisp/dists/quicklisp/software/mcclim-20161208-git/Examples/clim-examples.asd"


[A] I tried:
(asdf:load-system "/home/gwbennett/quicklisp/dists/quicklisp/software/mcclim-20161208-git/Examples/clim-examples.asd")
which resulted in:
Error while trying to load definition for system
/home/gwbennett/quicklisp/dists/quicklisp/software/mcclim-20161208-git/Examples/clim-examples.asd
from pathname #1=/home/gwbennett/quicklisp/quicklisp/:
   File #1# does not exist.
   [Condition of type ASDF/FIND-SYSTEM:LOAD-SYSTEM-DEFINITION-ERROR]

which now refers to a directory (#1=/home/gwbennett/quicklisp/quicklisp/) which does exist but, as far as I can see, contains only files
associated with quicklisp itself.

CL-USER> (probe-file "/home/gwbennett/quicklisp/quicklisp/")
returns:
#P"/home/gwbennett/quicklisp/quicklisp/"

Trying to follow Section 4.1 in suggesting the use of ~/common-lisp to store .asd files:

[B] I have copied mcclim's Examples subdirectory to ~/common-lisp/Examples and then
CL-USER> (asdf:clear-source-registry)
; No value

I have moved ~/.config/common-lisp/source-registry.conf.d/this-path.conf
to ~/.config/common-lisp/source-registry.conf.d/this-path.conf.old
since, if I read Section 4.1 correctly I should not need it now.

Now try
CL-USER> (asdf:load-system "clim-examples.asd")
which returns:
Component "clim-examples.asd" not found
   [Condition of type ASDF/FIND-SYSTEM:MISSING-COMPONENT]

(probe-file "/home/gwbennett/Examples/clim-examples.asd")
returns
#P"/home/gwbennett/Examples/clim-examples.asd"


[C] Try
(asdf:load-system "/home/gwbennett/Examples/clim-examples.asd")
which yields:
Error while trying to load definition for system
/home/gwbennett/Examples/clim-example.asd from pathname
#1=/home/gwbennett/quicklisp/quicklisp/:
   File #1# does not exist.
   [Condition of type ASDF/FIND-SYSTEM:LOAD-SYSTEM-DEFINITION-ERROR]


It does not matter where I move the file clim-examples.asd I always receive the Error message from [A] above referring to
pathname #1=/home/gwbennett/quicklisp/quicklisp/
Even if I move it into that directory, I receive this message. 

Thanks for any and all clarifications.
/Greg Bennett