I haven't tried the new update that just came out. But hopefully this will still apply.
I use it to tune acoustic guitars. I lay my iPod Touch in the curve of the upper bout. I play the string with conviction, let it ring for a few seconds, and then mute the note. The app doesn't announce the note until it stops. This also gets the tuning of the attack. The note can change through the decay, and I want the initial frequency. I tune from flat up to pitch, not down from sharp.
Hard to get into specifics without knowing what instrument you're tuning, but the app isn't all that finicky compared to a lot of hardware tuners believe it or not. What stumped me at first (and still catches me out from time to time) is that it doesn't announce the tuning until you mute the string. If you're new to tuning with a machine criticising every change, a few days practise and you should notice your efficiency increasing. Stick with it, it's a pretty solid app and it probably won't take you long to get the hang of it! Let us know what instrument you're working with and perhaps someone can get more specific.
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Some Tips
Hard to get into specifics
talking tuner more info