Here is a youtube video posted by Salesforce.com, about importing your data in the right order: If you are importing multiple objects that have dependencies, such as accounts and opportunities this video walks you through, step by step, which objects should be imported, and when.

 

http://www.youtube.com/watch?v=pozXkBMkSYM

 

Another great resource is the Answers forum https://success.salesforce.com/answers The Salesforce community, myself included, will help users that are struggling with Salesforce problems. Log in and post a question, or search through previous answers. It is all run by volunteers, so be nice, and you may be surprised how much help is offered!