How to be likeable at work
1. Call people by their name. People like to hear their own name. What they don't like is being referred to by their title, or not referred to at all. Calling someone by name makes him/her feel special, and shows that you're interested in him/her as an individual, not just in the context of a need. Extending requests or updates with an actual conversation can also be useful. For example, walking by someone's desk and shouting, "Hey, I need that report by end of day today" forms a much different impression than stopping by for a moment and saying, "Hey Bobby. How are you? By the way, could I have that report from you by end of day?"
2. Look for the positive in every situation. Pessimists don't win many friends. Bringing up your negative feelings about a situation, even though the situation itself might be unfavorable, is a sure way to alienate your coworkers and bring the entire mood of the establishment down. Instead, always look for the bright side. Make comments about the positive elements of each situation you encounter, and walk around with a smile on your face. This simple change will help people associate you with positive thoughts and positive emotions, and you'll be more well-liked as a result.
3. Avoid competition when possible. It's unfortunate but true that most offices in the United States are highly competitive environments. Workers are competing for promotions, for recognition, and sometimes just for pride. But the moment you come to be seen as a competitor, people will shy away from you and may even come to resent you. Don't create any unnecessary competitions, on a small scale or large scale. For example, don't go out of your way to claim credit for a group project, don't sabotage anyone, and don't try to squeeze someone's hand extra hard when you shake their hand.
4. Provide help, and ask for favors. Humans are social creatures, and we get along by helping one another. We're evolutionarily programmed to recognize and feel better about the people who help us as well as the people we help. As a result, the more you help other people--and the more they help you--the stronger your bonds will become and the more likeable you'll be. Go out of your way to help people who need your assistance, and never be afraid to ask for a favor of your own.
5. Touch people. Some modern offices have become touchless, thanks to occasional forms of inappropriate touching getting in the way of actual business. But appropriate touching, between you and the people you're comfortable with, is a way to break down the physical and emotional distance between the two of you. Shake hands whenever you greet someone, and touch shoulders to show empathy, give support, or solidify a point you're making. Just don't overdo it, or you might look like a crazy person.
6. Get past the small talk. Small talk is office fodder, and it's unfortunate that it passes for real conversation. You might be perfectly content talking about the weather or your local sports team, but those types of conversations won't win you much long-term favor. If you want to make a great impression and earn more likeability, you have to move past it. Ask genuine, down-to-earth questions of your coworkers when you have time to chat. Ask about their families, their hobbies, and their passions. You'll be surprised how much you never knew about the people you work with, and they'll like you better for having learned it.
7. Be consistent. You don't have to become a predictable robot, but adding consistency to your behaviors and routines is important. People need to know what they can expect from you, or else they might immediately write you off. Using some of the above strategies as examples, you can't be positive one day and negative the next--you have to be positive most of the time. You can't have a meaningful conversation one day and then revert to small talk the next--you have to be consistent.
For most of my audience (myself included), professional integrity is more important than popularity in the workplace. If taking an action that will make you more liked will compromise your work on a project, it's more than worth taking the hit in popularity. But if you can continue to do your job well and earn some extra warmth in the process, you might as well. Being well-liked means you'll work better as a team, you'll have more help when you need it, and you might even have a better chance at getting that promotion if there's an office full of people rooting for you.