http://dev.mysql.com/doc/refman/5.0/en/innodb-tuning.html
http://dev.mysql.com/doc/refman/5.0/en/server-parameters.html
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html
On mac, copy macport mysql config file my.cnf to right location

cp /opt/local/share/mysql5/mysql/my-large.cnf /opt/local/etc/mysql5/my.cnf

and add following changes

innodb_buffer_pool_size = 256M
innodb_additional_mem_pool_size = 20M
# Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 64M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 0
#innodb_lock_wait_timeout = 50
innodb_doublewrite=0
innodb_support_xa=0

in /opt/local/var/db/mysql5, delete ib_logfile0 & ib_logfile1, since we changed log file size to 64M.

to start stop server

sudo /opt/local/share/mysql5/mysql/mysql.server start
sudo /opt/local/share/mysql5/mysql/mysql.server stop