Stealth is an important part of tracking and hunting. It's a fine art, and like everything, takes practice. Stealth is used by military forces and is known as fieldcraft. Though you (probably) won't be sneaking around in the undergrowth wielding a sniper rifle or scrambling over enemy lines their techniques can be employed in tracking wildlife
Let's start with the obvious, if you trying to be stealthy you won't pull it off very well if you walk around in bright clothing, especially in the country or woods, surrounded by a wide variety of browns and greens. So, tone down. Wear muted colours that won't stand out and try to avoid wearing trousers and jackets that make a lot of noise whilst you're walking or else the animals will be able to hear you a mile off!
When you're approaching the animals it's important to reamains conceled or else they'll leg it, so, first thing to remember is try to avoid approaching any form of wildlife from a point where you are visible against the skyline, if you do then you'll stick out a bit like a sore thumb!
Another thing, stay downwind when you get close! Always try to have the wind blowing in your face or else the animals will smell you....if you struggle when detecting which way the wind is blowing then carry around a little talcum powder, chuck a bit in the air and it will tell which way the wind blows, simple.
In "stealth mode" the aim is to be as silent as possible (hence the word stealth) so learn to walk as quietly as you can, though this way seem impossible if you are trying to creep along a path covered with dead sticks that seem to snap very loudly it is acheivable, you just have to have the right technique. It's also useful to be determined (or just plain stubborn) and have bags of patience. Trackers, when approaching animals may have to even crawl along on their hands and knees or even wriggle along on their bellies! (Try it yourself, it isn't as easy as it looks).