In most of the companies, schools and colleges Google search queries by the internet users are under the mercy of network administrators and managers.
Most of the network administrators and managers can have access to the gateway or router within the company, school or college which will route your packets to the internet. There are many tools which would help to decode the the data being send and received through the gateway machine.
To hide your private Google search queries you need to use an encrypted channel for searching with Google. I would like to through light on the advantage of using Google services to make your Google search queries hidden from network administrators and managers.
The best option would be to use the Google Secure Search (with SSL) for making all your search queries.
In this case the communication between your browser and Google server will be encrypted. Enjoy making private search queries using Google!