How to copy a formula from one cell to many in Excel?

Example 1
Assume you have a formula =sum(A8+A9)
To copy this formula, do the following!

Change the formula as =sum($A$8 + $A$9)
Now copy and paste. 

Example 2 
Assume you have a formula =B3 * 5 / SUM(B4:B7)
To copy this formula, do the following!

Change the formula as =$B$3 * 5 / SUM($B$4:$B$7)
Then copy and paste. 

Example 3
Assume you have a formula =COUNTIF(C2:C4,A2)
To copy this formula, do the following!

Change the formula as =COUNTIF($C$2:$C$4,$A$2)
Then copy and paste.