How do I enter "ř" (small R with caron) and other unusual special characters on the iPhone?
That character is not accessible from the English iPhone keyboard. You can, however, enable other keyboards on your iPhone.

Under the Settings app, go to General then Keyboards and select the Keyboards control. You can then touch Add New Keyboard… and add the Czech keyboard as an option.

When typing, if you want to access theř key, hold down the globe key on the bottom row of the keyboard, select the Czech layout, and then when you press and hold r, you get the menu wherein you can select the ř.

If you frequently need Czech accents, keep the Czech keyboard installed. If this is a rare occurrence, you can then uninstall the Czech keyboard from Settings » General » Keyboards » Keyboards.



The easier way to access the ř character on a one-time basis would be to visit this page with your iPhone, copy the ř character, and then paste it into your friend's Contact information.