Here is how I have installed Oracle Client 12.1.0.1 on Windows 8. Official documentation can be found in Oracle® Database Client Installation Guide
12c Release 1 (12.1) for Microsoft Windows.

First download installation media from OTN and unzip into a staging area (assuming 7-Zip is installed in defaut location):

c:\temp\oc>"c:\program files\7-zip\7z" x winx64_12c_client.zip

7z output should end with:

Everything is Ok

Folders: 658
Files: 1144
Size:       930848229
Compressed: 915831969

Open a command window cmd.exe in administrator mode and to install Oracle Client with Administrator option in C:\oracle\oc121 directory run:

cd client
setup -silent "ORACLE_BASE=c:\oracle" "ORACLE_HOME=c:\oracle\oc121" "oracle.install.IsBuiltInAccount=true" "INSTALL_TYPE=Administrator" "oracle.installer.autoupdates.option=SKIP_UPDATES"

This command displays a new window named "Oracle Universal Installer" where a lot of messages starting with "INFO:" are displayed.
Make sure that in this new window the following ending messages are displayed:

The installation of Oracle Client 12c was successful.
Please check 'C:\Program Files\Oracle\Inventory\logs\silentInstallXXX.log' for more details.
Successfully Setup Software.

Check installed version of SQL*Plus:

c:\temp\oc\client>c:\oracle\oc121\bin\sqlplus.exe -v

SQL*Plus: Release 12.1.0.1.0 Production

If you want to test connection to your 12.1 container database (CDB) named cdb12c running on host ol6twsf, first create a common user named c##admin with:

SQL> create user c##admin identified by admin;

User created.

SQL> grant dba to c##admin;

Grant succeeded.

Check that ol6twsf listener is started on default Oracle Net port 1521 and has the right container database service that has the same name as the CDB:

[oracle@oel6twsf ~]$ lsnrctl status

LSNRCTL for Linux: Version 12.1.0.1.0 - Production on 29-JUL-2013 19:08:20

Copyright (c) 1991, 2013, Oracle.  All rights reserved.

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 12.1.0.1.0 - Production
Start Date                29-JUL-2013 19:00:59
Uptime                    0 days 0 hr. 7 min. 21 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Log File         /u01/app/oracle/diag/tnslsnr/oel6twsf/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oel6twsf.localdomain)(PORT=1521)))
Services Summary...
Service "cdb12c" has 1 instance(s).
  Instance "cdb12c", status READY, has 1 handler(s) for this service...
Service "cdb12cXDB" has 1 instance(s).
  Instance "cdb12c", status READY, has 1 handler(s) for this service...
Service "pdb1" has 1 instance(s).
  Instance "cdb12c", status READY, has 1 handler(s) for this service...
Service "pdb2" has 1 instance(s).
  Instance "cdb12c", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@oel6twsf ~]$

Check connection to cdb12c database instance with tnsping and Easy Connect syntax (hostname:port number/service name):

c:\temp\oc\client>c:\oracle\oc121\bin\tnsping ol6twsf:1521/cdb12c

TNS Ping Utility for 64-bit Windows: Version 12.1.0.1.0 - Production on 29-JUL-2013 21:02:08

Copyright (c) 1997, 2013, Oracle.  All rights reserved.

Used parameter files:
c:\oracle\oc121\network\admin\sqlnet.ora

Used HOSTNAME adapter to resolve the alias
Attempting to contact (DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=cdb12c))(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.70)(PORT=1521)))
OK (10 msec)

Now you can connect to database instance and to CDB root database:

c:\temp\oc\client>c:\oracle\oc121\bin\sqlplus c##admin/admin@ol6twsf:1521/cdb12c

SQL*Plus: Release 12.1.0.1.0 Production on Mon Jul 29 21:05:45 2013

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
    CON_ID
----------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
         0

PL/SQL Release 12.1.0.1.0 - Production
         0

CORE    12.1.0.1.0      Production
         0


BANNER
--------------------------------------------------------------------------------
    CON_ID
----------
TNS for Linux: Version 12.1.0.1.0 - Production
         0

NLSRTL Version 12.1.0.1.0 - Production
         0


SQL> show con_id

CON_ID
------------------------------
1
SQL> show con_name

CON_NAME
------------------------------
CDB$ROOT