Each specific item must be evaluated from the point of view of the context where it was found, and also in relation to other information on the same subject, either from Internet or from a database, periodical etc. Information from a source generally considered of good quality, which coincides with what is learnt from other sources, can be considered accurate. Final verification depends on somebody going out into the field and confirming the information via observation or personal contact.
How to acquire information step by step:
Ask questions: If you come across or are offered competitive information and believe that it may be confidential or proprietary ask questions to find out how the information was obtained, or why it was made available.
Be ethical: How would you or your business react if you found out that your competitors were receiving the kind of information that you acquired?
Breaking the law has consequences: Breaking the law can also result in adverse publicity to your company. Think about how you'd feel if your actions were publicly disclosed on the front page of a newspaper.
Regardless of what method you use to collect competitive intelligence, if you have any question as to the legality of your activity, err on the side of caution and chose another method!