How do you dilute a concentrated solution?

It really depends on what type of solution you are dealing with.

However by definition any solution that is less pure or takes up a smaller perecentage of the whole is diluted. Anything that will make the total amount of solution you currently have become a smaller percentage of the whole. Ex: When you begin with solution A and have 100 mL it is 100%. If you mix in 100mL of solution B the total solution is now 200mL and it is 50% solution A and solution B. It is now diluted.