As far as confidence calls here for me, crows are the best. I always call crows to the stand. It's amazing how well these dang things can hear and how worked up they can get. I wish all coyotes were as aggresive as crows are coming to a distress call. A squirrel chatter is also very good. Sqirrels are oftentimes the "watchdog" of the woods. When something is going on, they'll run up a tree or out onto a limb and start giving it heck.
There's a tip in there, listen for the crows, jays, or squirrels in the distance. Many times if you hear a squirrel chattering, or see crows wheeling overhead somewhere in the distance, look sharp! A critter is on the way to the call. I've repositoned to have the right angle just because I've heard a squirrel chattering from a direction that wasn't quite right for a steady shot as I sat. Listening to the animals allowed me to do this before the predator was within sight or spooking range. If I had ignored the hint the squirrel or crows were trying to give me, I probably would have been caught offgaurd and handcuffed.
The oldtimers may remember a post I placed on the old Shade Tree (that was a while back, huh!) forum. It was titled "Natures Calling Seminar" and told of how I heard a squealing distress sound one day as I was scouting some calling territory. I slipped on the sound that was coming from a deep hollow. After a bit I stalked close over the brow of the ridge and could see a little Sharp Shinned Hawk that had tackled an unusally large prey for it. Sharp Shinned Hawks are fairly little fellows and hunt other birds, nearly always small song birds, woodpeckers, ect... Well this guy got the big eye and tackled a full grown Pileated Woodpecker. The little hawk was riding the big old woodpecker bronc busting style. Grappled onto the woodpeckers back by his talons, the hawk was trying to reach around and bite the head and neck of woody for the kill. Woody was ducking and flopping his wings and crying steadily. Non stop in fact! This little show went on for several minutes when my Dad came sneaking (not all that sneakily) over to me. Dad had heard the crying of the Pileated and actually thought that I had found a good spot to call from and just set-up and was wailing away. It sort of made him mad that I didn't take time to inform him and set-up properly so here he came to chastice me. Well, he spooked the hawk and woodpecker. Showing great strength the Sharp Shinned picked up that big old woodpecker and flew it on down the hollow about fifty yards. When they landed the screaming of the woodpecker immediately started over again. That continued for about five more minutes or so and then stopped. I stayed around for another several minutes hoping that by chance their commotion might actually call a coyote. It didn't but Dad payed me a great compliment when he said that the bird sounded exactly like one of my call sequences. I think that the tone and rythem probably were the same, except I take pauses for a couple of minutes when calling. But I keep the calling fairly busy, without too long stops. I like to keep a critter interested and on the string to the stand. Doing so doesn't allow them to get edgy and begin that looping circle to cut the breeze. At least that's my thought regarding that. That when using the higher pitched sounds. When I'm using a courser sound or a fawn deer bleat/distress I don't call with the same fast cadence.