Infact, a NYTimes story suggested that the false-positive filtering rate of GMail is around 3% which means that every 3 emails (out of 100) tagged as spam by Google Mail may be from your friends, family or other contacts.
The next important question is how to catch these "GMail false positives" when you have tons of email in the Spam folder ? Well, it is not so tough as you may think.
First, turn on the Personal Level Indicators in GMail from the Settings page. When switched ON, these indicators add a single arrow ( › ) to messages that have your email in the To or CC field, and a double arrow ( » ) to messages that are sent only to you.
If you 20 or 30 email messages in the Spam folder, these indicators can help you quickly identify messages that were addressed to you. Look at the subject text or the sender's name - if that resembles a known contact, move that message from Spam to Inbox.
The above trick works just perfect for people who receive manageable amount of spam each day.
If your email address is more popular and you get hundreds of spam emails, try a search filter as described below [It is based on a simple theory - unlike friends or business contacts, a spammer is less likely to address you with your real name (or even pet name)]
in:spam to:me your_name
Type the above query in the GMail search box and it will show all spam messages that are addressed to you and have your name either in the subject or in the message body. [Replace your_name with your first name or even your pet name]
You'll get a list of emails that fit the above criteria - apply the same "personal level indicator" rule to visually identify non-spam messages from the search results.
Related: Tricks to hide your email address from spammers