One of the quickest ways to negatively inflate/skew your Google Analytics data is to include internal company site traffic.
Many companies have their Web site set as the home page in their Internet browsers (Internet Explorer, Mozilla Firefox or Google Chrome). Every time an employee opens their browser to surf the Internet, the company Web site comes up.
It’s not just visits that gets skewed. Your bounce rate shoots up and your average time on site goes way down. Plus, your home page traffic is not going to be proportional to the traffic on other pages of your site.
It’s easy to filter out your internal traffic. Here are 4 simple steps:
1) Find out your network’s IP address. Depending on company size, you may have multiple IP addresses. If you have an IT person, ask him. If you don’t have someone, go to www.WhatisMyIP.com. As soon as the site pulls up, you should see “Your IP Address Is:” and a number that looks something like “72.135.156.44″ directly below it. This is your IP address.
2) Login to your Google Analytics account. At the bottom right corner of the page you should see a “Filter Manager” link. Click it.
3) Click on “+ Add Filter” in the top right corner (denoted by the red arrow below)

You’ll be taken to a “Create New Filter” page.

Give your filter a name. I called my “Exclude company traffic.”
Since we want to exclude traffic from our IP address, select “Exclude,” “traffic from the IP addresses,” and “that are equal to” in the three dropdown menus.
Enter your IP address. Mine was “72.135.156.44.”
Select which Web sites you want to filter by clicking on the appropriate Web site profile(s) and then clicking “Add>>”
Click “Save Changes”
4) You’re done! Sit back and relax knowing that your Web site traffic activity is a little more accurate.
If you’re smart, you’ll exclude your marketing team’s IP address as well in case they want to inflate the numbers in an attempt to show how good of a job they’re doing.
Additional resources: Google Analytics has a good help page with more information about excluding internal traffic.