The sound ř, a trilled r and a ž on top of each other, is distinctly Czech. It is often the last sound to be mastered by Czech children and foreign learners of the language alike. It is easiest to learn to pronounce it when it appears in the middle of a word surrounded by vowels. In this context, the ř can at first be fudged as the simple combination rž. Practice with such words will hopefully lead to a smooth fusion of the consecutive sounds r + ž into a true ř. Practice the following words. Start with a r + ž sound and then try to move on to the more genuine ř which the speaker pronounces.
nahoře (=up above)
In other contexts, it is more difficult to fudge the ř into r + ž. Practice these words.
řízek (=meat cutlet)
dobře (=good, well)