Where are you at in Idaho? I have only taken four bulls with a bow so I know others have great advice here.
You mentioned calling. It is fun and it works sooo well on the dvd's but just doesn't pan out the same on public land. Call sparingly and make sure it sounds elky when you do.
Where I hunt, most elk sounds are produced by people. We have called in a lot of hunters when we answered their calls. More than once, we have watched them sneaking in, and we eventually run off through the woods breaking branches. I would sure like to hear their story on Monday about how they almost got on elk.
If you get a bull to talk and you are sure it is an elk, run to him (literally). Close the distance fast because there's a good chance he is already heading away from you. One time I was jogging towards one and luckily saw his antlers coming toward me before he saw me. I ducked down and shot him when he came past. So be prepared for anything when you are on the run.
If you know you are in elk, slow waaaay down. If you are not on fresh tracks or sign, cover lots of likely ground until you get into it then slow down.
Just a couple lessons that have served me well. Spent way too many years figuring it out.
I am up in Grangeville, but have generally hunted out of the Council - Weiser region.
good luck,
oxnam