As with any industry there are going to be people who are fake.  This is unavoidable and the best way to keep yourself from being taken is to stick with practitioners who have earned good reputations amongst collectors.  Unfortunately because of unscrupulous sellers writing bad things about the competition all over the internet the best way to truly get an accurate portrait of a practitioner is to contact their clients.  With eBay, you can see their clients in their feedback, and with websites if they have a forum you can join and see what the response & atmosphere is like on their site.  To see if a spirit is truly with you the best way is to trust your gut instinct & your natural senses to see if you detect an additional presence with you.  It can be difficult to put the trust solely in yourself, but by doing so you are gaining the strength & ground to build your own abilities & sensitivities.  Don’t dismiss even the smallest of paranormal occurrence as sometimes spirits introduce themselves gradually rather than being immediately in your face.