"I was thinking about you."
It's not their birthday, you don't need to borrow money from them; you didn't wreck their car... you have just been thinking about them. Do you know how powerful of an impact that has, just knowing you were thought of? Wow.

"So how are you?"
Really ask this question. It's not a lead in to your tirade about the latest annoyance; it's a genuine interest in how they are. And if they go on some tirade, be there to listen. It's the perfect, powerful follow-up to "I was thinking about you." Being interested in how they are really does show how much you were thinking about them.

"Here's what's up with me."
Okay, so now it's your turn. You don’t have to bog them down with details or be too vague either... just include them in your life. Get them caught up about you, with you. Share you.

"What do you think about...?"
Creating the ties that bind… getting their opinion about something in your life; finding commonalities... growing together.

"I love you."
Go ahead, say it. You did call someone you loved and who loves you back, right? Even if you've never said it before, say it now. Those three words alone are more powerful than the rest of the conversation.

You've basically said it by calling them, so go ahead… say it.