To establish POV, you need to get the reader inside the character's head. In essence, the reader becomes the POV character. The reader knows the character's thoughts, and experiences the world through the character's senses. In the two scenes that follow, notice how the reader is immediately clued into whose head she is in.

Scene One

Sarah walked into the kitchen, the smell of bacon and the familiar sound of the sizzle had her mouth watering, and she hoped her roommate was in a sharing mood. “Hey….” Sarah stopped short at the sight of her ex-husband standing over the frying pan, a piece of bacon dangling from a raised fork.

It had been six months since she'd seen him, and blasted if his hard body didn't look scrumptious in his tight jeans and black T-shirt. Good enough to eat. Her heart hiccupped at the same time her stomach growled. But then she remembered why she left him. “I don't know how you got in, but you obviously know where the door is. Use it.” She paused a minute. “You can leave the bacon.”

Scene Two (Same scene written in different POV) Mark heard the footsteps padding down the hall, and felt certain the smell of breakfast would lead Sarah to the kitchen. The old adage about the way to a man's heart was through his stomach wasn't just true for men. Cooking for Sarah had been how he'd won her heart the first time. But could he do it again? Hell, it would be a lot easier if he understood why she left him.

“Hey…” Suddenly she was there and still as beautiful as he remembered. Shock widened her eyes, and then her gaze whispered up and down his body. Right then something else flashed in her baby blues. Hunger. And it wasn't just for the bacon. Maybe paying her roommate a hundred bucks to leave was going to be worth every cent.

Sarah blinked, and just like that, all the wanting left her expression. “I don't know how you got in, but you obviously know where the door is. Use it.” She paused a minute. “You can leave the bacon.”

One trick to establishing POV is to use one of the five senses: sound, touch, smell, sight, or taste. When a character experiences one of the senses, the reader automatically slips into that character's point of reference.