Best Configuration (my.cnf) For MySQL?

my.cnf configuration

What should be the best configuration(my.cnf) for MySQL in this server :

AMD Athlon(tm) 64 X2 Dual Core Processor 4200+
cache size: 512 KB
speed: 2200.246 MHz
4GB RAM DDR2
350 GB HDD

my current my.cnf contains this :

[mysqld]
set-variable = max_connections=500
set-variable = max_user_connections=100
set-variable = wait_timeout=100
set-variable = interactive_timeout=100
set-variable = local-infile=0
query_cache_limit=30M
query_cache_size=64M
query_cache_type=1
max_allowed_packet=30M
old-passwords = 1
skip-networking
[client]
port = 3306
socket = /var/lib/mysql/mysql.sock
[mysqld]
port = 3306
socket = /var/lib/mysql/mysql.sock