Brandi,
I had that same problem and worked on spinning over the winter. Now when I get to a hill I break it down:

Get into a good spin and high speed before I hit the hill.

Down shift BEFORE it gets too hard to pedal because that's where I loose all my speed and momentum.

I find the right gear to spin easy and I concentrate on form: back flat, spin smooth, etc. I may start humming to myself, pick a spot to concentrate on several feet ahead of me and enjoy the ride. If I look at the top of the hill I tend to mash and it's mentally tougher for me. The hills I did yesterday I used to ride around 6 mph and now I'm between 8-10, so yes, practise does help.

Of course, I'm a newbie at this as well, but I've found this to work for me. And before I hit the hill, I'm already chanting to myself "I LOVE hills, hills ROCK, I OWN this hill" and I'm to the top before I know it.

Just have fun with it!