Table optimization ideas needed

Hi all,

I made a post a week ago to ask for the idea of the fastest way to get 
table records.
Fyi,
http://phparch.cn/index.php/mysql/35-MySQL-programming/126-fastest-way-to-get-total-records-from-a-table

Look at the time even a 'count(1)' taken.
Then you can imagine how much time sql such as "select a,b from 
table_name where c='d'" will take.

I have a lot of tables like that. So my questions is:
What's your practice to optimize tables like that?

Thanks in advance.

-- 
Regards,
Shelley