Being interested in others is much better than trying to get them interested in you. The personal pronoun "I" is one of the most commonly used words for a reason - people love the focus being on themselves.
Being grateful to and interested in others does much more than seeing them as potential marks or suckers. It can also take the form of:
Greeting people when going by with enthusiasm, since it shows interest in their presence.
Showing concern and interest in seemingly unimportant, or oft-overlooked people.
Expressing admiration to those we admire or respect.
Wish them a happy birthday!
Show interest in their problems and wanting to learn more. Don't need to be able to solve it.
Making friends means putting ourselves out there to do things for others, things that take time, energy, unselfishness, and thought.
Just make sure it's sincere. That's what makes it mutually beneficial and not a skewed manipulation.
One's expression is one of, if not the, most important parts of our appearance. Especially ones smile. Just make sure it's real and not insincere. It must be real and given away for a good reason.
This effect even carries over when talking over the phone, since the enthusiasm is expressed in the tone of voice and word choice.
If you have a good time meeting others, as shown through a smile, then they'll be able to have a good time meeting you.
If you don't feel like smiling, forcing yourself too will make happy feelings follow. Happiness relies on what one is thinking about and their perspective, whatever their situation and thoughts are.
Have a system to remember others' names or any way to recall them. People love hearing them and it's a subtle yet effective compliment. But forget or misspell it and it'll be an insult, so be certain.
Take the needed time and energy to concentrate on and remember names. Create mental connections between someone's face, appearance, or characteristics and their names so they're easier to recall.
If you don't get the name distinctly, say you didn't hear it clearly and ask for it again. If it's unusual, ask how it's spelled. Try to repeat it several times to improve the association. Write it on a piece of paper, concentrate on it for a while, then tear it up.
Another way to get this effect is to name things after people.
Most people only want an active listener about a topic they enjoy and/or to expand their ego. Listen out of genuine interest, not insincerity, and encourage them to keep talking. Genuine, rapt attention has lots of implied flattery. Ask questions you know they'll enjoy answering.
Exclusive attention is vital - looking at phones will break this. Be patient and empathetic, since this all adds up to show how important this person must be since they're worth listening too. It all adds up to a feeling of importance again.
The opposite effect is not listening for long. Interruptions, bringing the convo back to yourself or doing both at once, all lead to someone disliking you.
Find what someone is most passionate or interested in, and bring them into a conversation about it. Do some deeper research if you can. It could be a broad topic or a specific incident/memory they love sharing.
Even if you intended to see someone about an entirely different topic, focus on their interests first helps it go much smoother and "warms them up." Avoid asking directly and bring it to their passions first. It ultimately pays off well for both parties.
Find something you honestly admire in another and share it with them. It works since it follows the universal law of human relations: make the other person feel important. People want approval, appreciation, and sincere recognition of their true worth, as they all consider themselves important. Recognizing it subtly can work wonders.
Sometimes assuring someone of their worth and importance can even be life-changing. People may be starving for some recognition, and recognizing it and talking with them about it may be priceless.
We don't need to do this just to get something from another. It can just be to spread some extra happiness around. This rule can (and should) be followed at all times in all places.
This can be done by assigning other people important roles, jobs, or symbols. Or simply showing respect for them and what they do.
Useful, simple, everyday phrases that help communicate this are:
I'm sorry to trouble you, ...
Would you be so kind as to ...
Won't you please?
Would you mind?
A good rule to remember is every person you meet is your superior in some way, and in that way you can learn from them.