hill repeats are bar none the "best bang for the buck" I've found for moving in the mountains, add a pack for more resistance
usually with enough cardio, you don't have to count calories much
+1 on loading up a pack and hiking the hills. One of the best things you can do leading up to the season. Use a bunch of water bottles and bladders in the pack, that way if you need to you can dump weight towards the end of a hard hike.
As far as calories, there's a very interesting article in this month's Scientific American on how humans burn calories. They report on a few studies where they've accurately measured actual calories burned by having people do different levels of exercise , giving them carbon isotopes, and very accurately measuring CO2 production.
What they found was surprising--no matter the activity level, humans who did vigorous exercise only burned a few hundred calories per day more than those who didn't. The theory is that humans have evolved to shut down other calorie-consuming physiological processes to offset the calories burned by exercise, one of them being inflammation.
I'm not sure I believe it 100% because every backpack hunting trip I go on leaves me several pounds lighter. Interesting nonetheless.
