Rydiu is right that choosing the correct word is important; however, he is wrong in the word he chose. Every style guide I can find indicates that "ensure" is the proper word.
Here are a few examples:
http://www.westmont.edu/_news/pages/sty ... nsure-2821
ensure, insure, assure
Use ensure to mean guarantee or make certain. Steps were taken to ensure the document's accuracy. WRONG
Use insure for references to the characteristics of insurance: The policy will insure your home.
Use assure to give confidence or to inform positively: She assured him that the decision was a wise one.CORRECT
http://www.oea.umaryland.edu/communicat ... guide.html
assure, ensure, insure -
Assure means to give confidence. Ensure means to make certain or guarantee. Insure means to contract to pay or be paid money in the case of a loss.
http://www.law.wisc.edu/shared/styleguide.htm
assure, ensure, insure
A person assures (makes promises to, convinces) other persons and
ensures (makes certain) that things occur or that events take place. Insure means to establish a contract for insurance of some type. Any predicates beginning with that should be introduced by the verb ensure, if the verb is in the active voice. [Garner, Dictionary of Modern American Usage]