Changing positions often - not every 2 minutes - in bed could be really satisfying for both partners, as diversity may strike you and let you feel or discover new things, new ways in which you can have each other and new sensations. The way you change positions could also be very erotic; try to avoid sudden actions and be careful not to get injured. Anyway, try to stay on top of the situation at all times and lead her firmly to the new position; let her know there is a strong, determined man there that knows what he's doing and she'll focus on what she feels and what you want her to feel. Any other way and she'll be concerned with other things and it'll be harder to get her to orgasm.
Pillows - the great handy accessory in any bed
They are always of great help as you can slide one under her thighs so that she can open up easier to you. Also, they enhance their sensations, as the G-spot located on the frontal side of the vagina can now be stimulated a lot easier. It helps a lot if your penis is slightly bent upwards. This position is also comfortable for her and now she can close her eyes to focus on what she feels, again in your advantage.
Have a seat as I eat you
A very erotic sensation for them is to let them dominate you just for a little while, so... be the perfect gentleman and invite them to have a seat on your face. Try to make it easier for them and get close to a wall or something they can use as support. If you have a good technique they might lose their balance even if they lean on the wall.
Deeper penetration, stronger moans
Here's one of my favorites... As you're over her, changing positions, drag her to the edge of the bed, spread her legs wide open and ply her legs toward her shoulders and a bit upwards. You'll never penetrate her deeper than this and you'll see how her eyes get wider and stare at you, through you, loosing sense of reality as she's focusing on what she feels in that moment.
You can always return to your favorite position, but try to alternate rhythms, moods, rooms, positions, clothing... the sky is the limit when you have an open relationship with your partner and you trust each other.
