How to secure the segment passed by the user?

[eluser]FlyingCat[/eluser]
Hi guys. I was wondering what are the best practice before sending segment to the Model.

For example:

Get the segment1 from
base_url/controller/query_detail/segment1

on my controller

Code:

public function query_detail($segment1)
{
//what are the best practice before I send the segment1 to the Model?
   $this->load->model('model');
   $this->model->query($segment1);  
   ......  
}

I hope I explain well. Thanks for the help.