Keep your application straight forward
The one simple way to make recommendation letters contribute to your admission process is to keep your application straight and honest. Present the facts as they actually are - be truthful about every claim you make in every aspect of your application.
There is one thing that you certainly can do and that is to choose the people who can recommend you judiciously. Choose a person who knows you well and likes you as a person and then ask him/her to give a fair assessment of you as a person in the recommendation letter.
Your application form will give you details about the recommendation letters you are required to submit. The number of recommendations and from whom - whether from your work or from your school or both.