Rackspace have created a script that can be used to test and provide guidance to tuning mysql. Oneliner:
The following one-liner is for those who have not downloaded mysqltuner before:

wget https://raw.github.com/major/MySQLTuner-perl/master/mysqltuner.pl; chmod +x mysqltuner.pl; ./mysqltuner.pl

If you would like to download and change the permissions in individual steps follow:

wget https://raw.github.com/major/MySQLTuner-perl/master/mysqltuner.pl

chmod +x mysqltuner.pl

Then run the script with:

./mysqltuner.pl

Your output should look similar to:

[root@linux~]# ./mysqltuner.pl

 >>  MySQLTuner 1.4.0 - Major Hayden <[email protected]>
 >>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
 >>  Run with '--help' for additional options and output filtering
[OK] Currently running supported MySQL version 5.1.73
[OK] Operating on 64-bit architecture

-------- Storage Engine Statistics -------------------------------------------
[--] Status: +CSV +InnoDB +MRG_MYISAM
[!!] InnoDB is enabled but isn't being used
[OK] Total fragmented tables: 0

-------- Security Recommendations  -------------------------------------------
[!!] User '@bash-test' has no password set.
[!!] User '@localhost' has no password set.

-------- Performance Metrics -------------------------------------------------
[--] Up for: 44m 11s (13 q [0.005 qps], 7 conn, TX: 16K, RX: 662)
[--] Reads / Writes: 100% / 0%
[--] Total buffers: 34.0M global + 2.7M per thread (1000 max threads)
[!!] Maximum possible memory usage: 2.7G (280% of installed RAM)
[OK] Slow queries: 0% (0/13)
[OK] Highest usage of available connections: 0% (1/1000)
[OK] Key buffer size / total MyISAM indexes: 8.0M/90.0K
[!!] Query cache is disabled
[OK] Temporary tables created on disk: 0% (0 on disk / 3 total)
[!!] Thread cache is disabled
[OK] Table cache hit rate: 53% (8 open / 15 opened)
[OK] Open file limit used: 0% (16/5K)
[OK] Table locks acquired immediately: 100% (18 immediate / 18 locks)

-------- Recommendations -----------------------------------------------------
General recommendations:
    Add skip-innodb to MySQL configuration to disable InnoDB
    MySQL started within last 24 hours - recommendations may be inaccurate
    Reduce your overall MySQL memory footprint for system stability
    Enable the slow query log to troubleshoot bad queries
    Set thread_cache_size to 4 as a starting value
Variables to adjust:
  *** MySQL's maximum memory usage is dangerously high ***
  *** Add RAM before increasing MySQL buffer variables ***
    query_cache_size (>= 8M)
    thread_cache_size (start at 4)