1. Be authentic: It's easy to spot a phony person. We've all experienced them. Cockiness, overly self-assured (read insecure), and just "not down to earth," are traits that hinder interpersonal relationships. We also know that it doesn't take long to unmask a person who likes to wear one.
2. Show respect: Everyone wants to be respected. It doesn't take much to be respectful of others. Listening goes a long way towards displaying respect, as does caring what the other person is relating to you. A "thank you," "how are you?" (and meaning it), and genuine concern for what's going on in the other person's life works wonders. In business...customer care and respect means return clients. In personal relationship, it means much smoother days.
3. Communicate: Talk about things. Find out how someone's day is going (or went). And...If something's bothering you and you don't tell the other person, it can wind up eating away at you until it (all too often) explodes. Ask questions, have dialogue, clear up (what may be) misconceptions. And...do it in a calm manner. Otherwise, you're not really communicating...it will seem like you're dictating.
4. Don't be a control freak: No one wants to be suffocated. We each have our own lives, even though we may be in a personal relationship or business partnership. I'd venture to say that a major percentage of relationships break up because one person is trying to control the other person (or people). Imagine living under those conditions. It has to be extremely excruciating. If you really care about a person - their happiness should come before your need to control them.
5. Be accepting: No two of us have the same likes and dislikes. And...we're only human. We make mistakes, like different foods, movies, music, beverages, people, clothes, and everything else. Plus, we live in a transient world. People come and go into our lives from different cultures and backgrounds. There's a beauty in that and a learning experience to be enjoyed. And...new and different relationships to be built. It's great (and expands your knowledge base) to have all different types of friends and/or clients.
6. Avoid selfishness: Sure we all need and want our own "stuff." That's to be expected. But, there's also something wonderful about sharing - not only our possessions, but our ideas and emotions as well. I'm sure the memory of someone sharing their lunch with you (when you were in school), or some other material thing, brought a smile to your face and made you feel good. Well...spread that feeling to others. It really does help in the building and maintaining of relationships.
7. Be trustworthy: Trust is the basic foundation upon which any and all relationships are built. If you can't trust someone, then how can you possibly have a relationship with them. Do what you say you'll do, or...tell the other person or persons why you can't. Going "behind someone's back," lying, or not being responsible, are the easiest ways to lose a relationship (regardless if it's business or personal).
8. Laugh: Always keep your sense of humor. Very few things are so serious that you can't laugh about them. Even situations that you take seriously today...there's a good chance that you'll be laughing about them tomorrow. Laughter is a glue that helps to hold friendships, business, and romantic relationships together. A good laugh is cleansing.
8. Be loving: Love is what life is all about. We search for it endlessly. Not having it creates all kinds of potentially deleterious behaviors in humans. Spread love. Telling someone you love them (whether it's your children, spouse, partner, or friends) is priceless...a true gift.