There is an art to building strong relationships in business. 
Unfortunately, most people never learn the art. Instead, they wear Hello, My Name Is name tags and attend big fancy networking events. They get hundreds of business cards printed and hand them out whenever possible. They approach relationship building with the mentality that "more is better."
In reality, that couldn't be farther from the truth.
As a result, these seven lessons are learned far too late in life.

1. One great connection is worth more than 100 forgotten acquaintances.

Having a Rolodex of names upon names of people you haven't spoken to in years (or spoken to ever) isn't valuable. At all.
What's valuable is having someone in your life you can count on for advice, for insight, for referrals, for introductions. Someone you believe is a good representation of who you are and what you do, and hopefully, someone to whom you embody those same characteristics.

2. Business relationships are built on actions, not promises.

Nobody trusts the person who says they can do something that never happens.
Tried-and-true business relationships manifest solely through action. When two parties agree to work together, and both deliver on their promises, trust is inherently solidified. 
Unfortunately, most people try to build relationships based on promises. They measure their value through the things they say they can do, opposed to what they actively and consistently deliver.

3. Positive relationships require constant nurturing.

You can't ignore someone for months and then reach out and ask them for a favor.
Building business relationships that last means taking the time to check in with people, to see how they're doing, to take an interest in their own goals and aspirations--and to understand what would help them the most in exchange. 
Business relationships are still relationships. And nobody wants to feel like they're being taken advantage of. They want to know that it's a mutual exchange.

4. You should always give more than you take.

In business especially, giving goes a long way.
Every time you ask someone for a favor, you should be offering to help them with something twice as often. Most of the time, people won't even need what it is you're offering, or will decline, but it's the gesture that shows how much you care. And in the moments when they do take you up on your offer to help, make sure you deliver. That's what they are going to remember most the next time you ask for something in return.

5. Talk numbers second. Talk value first.

Too many hungry people in business want the very first conversation to be all about the numbers.
They want to know how much they're going to make before they even think about the project. They want to sign contracts before they've taken a step into the work. And as a result, the message they're sending is they care more about their own self-interests than they do about creating something meaningful and delivering value to the project.
The best business developers and networkers do the opposite. They show and prove how valuable they would be by taking a few steps into the work, almost always causing the team members to willingly make an offer in return.

6. Your energy introduces you.

Just because you're "doing business," it doesn't mean you can't or shouldn't be personable.
In fact, the more likable of a person you are, the easier it will be for people to welcome you into their inner circles--and the more willing they'll be to help you out. 
It doesn't matter how talented you are, how well-connected or wealthy you are. Positive energy attracts positive energy. And if you want the doors of opportunity to stay open, then what's most important is that you always remain humble, grounded, and willing to learn and connect with those around you.

7. Business takes time.

Some of the best opportunities take months, or even years, to nurture.
Some of the best connections require a lot of giving in order to turn into a mutually beneficial relationship.
Part of maturing in the business development world is understanding that patience is as crucial as anything else. And in order to build sound relationships, you can't expect bonds to be formed overnight.