Talk and visit with people. Don't differentiate by position or standing within the company. Secretaries and janitorial staff actually have tremendous power to help or hinder your career. Next time you need a document prepared or a conference room arranged for a presentation, watch how many people are involved with that process (you'll probably be surprised!) and make it a point to meet them and show your appreciation.
Make it a point to arrive ten or fifteen minutes early and visit with people that work near you. When you're visiting another site, linger over a cup of coffee and introduce yourself to people nearby. If you arrive early for a meeting, introduce yourself to the other participants. At social occasions, use the circumstances of the event itself as an icebreaker. After introducing yourself, ask how they know the host or how they like the crab dip. Talk a little about yourself- your hobbies, kids, or pets; just enough to get people to open up about theirs and get to know you as a person.
Keep notes on people. There are several xxxcontact managementxxx software applications that are designed for salespeople, but in business, nearly everyone is a salesperson in some capacity or another. They help you create a xxxpeople databasexxx with names, addresses, phone numbers, birthdays, spouse and children's' names; whatever depth of information is appropriate for your situation.
It's a good idea to remember what you can about people; and to be thoughtful. Send cards or letters for birthdays or congratulations of promotions or other events, send flowers for engagements, weddings or in condolence for the death of a loved one or family member. People will remember your kindness, probably much longer than you will!