Have phones with a physical keyboard unlocking is usually done in the effect, similar to its inclusion. It is done by pressing certain keys in a special order, or by pressing and holding one of them. It can be the keys *, #, and press "Menu". Consecutive pressing two or more keys most securely protect the keyboard from unwanted unlocking.
The phones touch screen and keyboard, as such, no. It is the role of the screen. If the phone still has a few buttons (of the package and reject the call), they are locked together with the screen. To unlock these phones often need to press and hold a certain part of the screen that looks like a button (often with an icon in the form of a castle). This method allows quite well to protect the phone from unwanted unlocking.
In some models of touch screen phones a more serious way to unlock the keyboard. It lies in the fact that the screen needs to "draw" a polyline to a specific shape. This method has the highest reliability, as it is guaranteed to eliminate unwanted clicks.