How you break in new jeans depends on what outcome you hope to achieve. For many women, the jean of choice may be fitted (or skinny) jeans. Stretching out those skin-tight jeans so that you can walk without having that strait-jacket feeling might be the desired result. Stiff jeans, on the other hand, will likely have you wanting to soften them up. Whatever the case may be, here are some general tips that work for any jean.
Jeans are like baseball gloves. They work best when they've been worked a bit. Since creasing isn't much of an issue, go ahead and pound those jeans. Fold them up and slap them on the ground. Take a bat and swing for the fences.
Put on the jeans and go for a jog. Sounds a tad strange, but physical exercise is a sure-fire way of getting the pants to loosen up. Even a brisk walk should be sufficient. Just don't coddle those jeans by tip-toeing around and expect them to soften up.
If you do not mind fading, throw the jeans in the wash. Use warm water. Do not load them in the dryer. Instead, try air-drying with a light beating. Another trick is to put them on while wet and let them dry to conform to your figure.
Just like you would a poster, roll the pant legs up and let them stay that way for a while. Then, flip them over and repeat on from the other side. This is a great way to loosen up those stiff denim fibers.
The last tip is the most obvious one. There's no more direct way to break in new jeans than to simply put them on and go about your life. Besides the fact that it's easy, wearing your new jeans, after all, is why you bought them.