1. How is the fraction such as one third written as a decimal?

When doing the division 1.0000 ÷ 3, the answer 0.3333... is obtained.
To indicate that the "3" repeats forever a point is placed above the first 3 i.e. 

2. Using a calculator, how is a fraction changed into a decimal?

By division. Divide the top number by the bottom one.

3. How are percentages changed into decimals or fractions?

Changing percentages into decimals or fractions always involves dividing by 100.

4. Is it acceptable to write fractions such as one half as 1530 ?

While 1530 is equivalent to 12 final answers should always be given in their simplest form.