Disguises are very important part of the game, because thanks to them you can easier explore the inaccessible map areas or get closer to main mission targets. But unfortunately there is one very important difficulty connected to disguises - Hitman can be exposed by those dressed the same way. Importance of this problem can be however somehow reduced. The first of proposed solutions is a skillful choice of disguise. For example, if you've reached a warehouse with ten guards and two mechanics, it is much better to get a mechanic outfit, thus reducing chances of encountering person dressed the same way. The second of mentioned simplifications is to use Instinct. Every time when there is a risk of being exposed, you might hold Instinct key/button, trying to hide your identity. Usage of this method is highly limited on higher difficulty levels, so you should use it only as a last resort.
You can get disguises in two main ways. The more obvious option is to obtain them from stunned or killed enemies. It would be best to change your clothes only after hiding the body in some secluded place. Occasionally you can also find disguises in different places.