How to speed up the database query?

Hi everyone!

I'm looking for solution to speed up the database query, means that to get resultset as quicker as we can.

For example if I've 700 records in the table it will take longer time compared if I've only 20 records. How do we speed
upthe query?. Any query technique that can be applied?.
 

Thus wild card query like : select * from tableA will cause query time increased compare to say select a,b from
tableA.

any help, prettymuch appreciated.