How do we put a given number in scientific notation? list the steps?

For a positive exponent: 
step 1) Move the decimal place to the left to create a new number from 1 up to 10.               ex:312,000,000,000?since 312,000,000,000 is a whole number, the decimal point is at the end of the number: 312,000,000,000.

So, it then becomes 3.12.

step 2) Determine the exponent, which is the number of times you moved the decimal.
              ex: in this example we moved the decimal to the left so that tells us that our exponent will be positive and since we moved the decimal  11 times to make it a number that is greater than 1 but less than 10 our exponent then becomes 11  so it would then be 10 to the 11th   (if you moved the decimal to the right it would then become a negative)                                                                
step 3) Put the number in the correct form for scientific notation
              ex: (N x your exponent)    312,000,000,000 x 10 the the 11th (you would write that as an exponent tho)
step 4)