mysqltuner script to optimize my mysql database

I have a Dedicated Server running an php eshop.

The server is built on Debian 7.8 64Bit, and has 12 cores and 64GB RAM. I try to use the mysqltuner script to optimize my mysql database.

The current query_cache_size is set to 256MB. I am not sure I should continue increase this number as suggested or not.

Also,
A) could you tell me why the Query cache prunes per day(111209) is so high?
How can I to reduce this?
B) why the Table cache hit rate is only 56%
How can i achieve better cache hit rate?

MySQLTuner 1.4.0 – Major Hayden

Bug reports, feature requests, and downloads at http://mysqltuner.com/

Run with ‘–help’ for additional options and output filtering

[OK] Logged in using credentials from debian maintenance account.

[OK] Currently running supported MySQL version 5.5.43-0+deb7u1-log

[OK] Operating on 64-bit architecture

——– Storage Engine Statistics ——————————————-

[–] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MRG_MYISAM

[–] Data in MyISAM tables: 34M (Tables: 157)

[–] Data in InnoDB tables: 422M (Tables: 4)

[–] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17)

[!!] Total fragmented tables: 14

——– Security Recommendations ——————————————-

[OK] All database users have passwords assigned

——– Performance Metrics ————————————————-
[–] Up for: 12h 49m 55s (2M q [59.876 qps], 138K conn, TX: 6B, RX: 476M)

[–] Reads / Writes: 76% / 24%

[–] Total buffers: 32.3G global + 2.8M per thread (600 max threads)

[OK] Maximum possible memory usage: 33.9G (53% of installed RAM)

[OK] Slow queries: 0% (0/2M)

[OK] Highest usage of available connections: 1% (9/600)

[OK] Key buffer size / total MyISAM indexes: 16.0M/36.1M

[OK] Key buffer hit rate: 100.0% (1B cached / 17K reads)

[OK] Query cache efficiency: 70.2% (1M cached / 2M selects)

[!!] Query cache prunes per day: 111209

[OK] Sorts requiring temporary tables: 0% (223 temp sorts / 70K sorts)

[!!] Joins performed without indexes: 5298

[OK] Temporary tables created on disk: 18% (13K on disk / 72K total)

[OK] Thread cache hit rate: 99% (9 created / 138K connections)

[OK] Table cache hit rate: 56% (239 open / 423 opened)

[OK] Open file limit used: 0% (403/1M)

[OK] Table locks acquired immediately: 99% (1M immediate / 1M locks)

[OK] InnoDB buffer pool / data size: 32.0G/422.7M

[OK] InnoDB log waits: 0

——– Recommendations —————————————————–

General recommendations:

Run OPTIMIZE TABLE to defragment tables for better performance

MySQL started within last 24 hours - recommendations may be inaccurate

Increasing the query_cache size over 128M may reduce performance

Adjust your join queries to always utilize indexes

Variables to adjust:

query_cache_size (> 256M) [see warning above]

join_buffer_size (> 256.0K, or always use indexes with joins)