To do an assessment of anyone presumes that you know what a normal assessment is. While most students are taught what a normal assessment is in school, the fact is that very often many abnormal things go right by them when they are performing their actual physical assessment of patients! This, I believe, is due to inexperience with doing physical exams in the first place. You are so accustomed to seeing "normal" things that when something slightly out of the normal is in front of you, you'll miss it. As time goes on you get better at noticing them. For this reason it is best to use some kind of form or questionnaire when doing your first assessments with patients.
There is a sticky thread on the Nursing Student Assistance Forum called Health Assessment Resources, Techniques, and Forms (
http://allnurses.com/forums/f205/health-assessment-resources-techniques-forms-145091.html) that has a number of links to websites with information on how to do various types of assessments on patients. You'll want to go to that thread and explore those links. I just opened up and looked at one of the health assessment links for a child just last week and found it to be quite extensive. While you may not find an exact form that you need, you should be able to find enough information from the links posted there to put together your own form to use.
After doing an assessment on a patient, go back through the form or set of questions you have used to see if you captured everything about the patient. If you find something got left out, add it to your form right away for the next time you do an assessment or interview.
On this post is a list of what I feel are important items that need to be extracted from a patient's medical record (chart) as well: http://allnurses.com/forums/2228927-post5.html