I've found a good way to learn to pronounce certain words or consonants is to download the word to your computer and assign the sound to an action you do often on your computer. For instance, I had difficulty learning to say tři and ctyři. So I downloaded them from a website and then went to control panel in sounds and assigned them to a function. For example, I assigned tři to the start function. Every time I clicked on the start, I would hear the word tři. I did this at work so I clicked on it several times a day. I assigned ctyři to another function such as opening an email. So every time I opened an email, I heard the word ctyři. It's amazing how hearing the word over and over can help you say it. Before I knew it, I could say it right. I guess that's how we learn as children right? Now I have to assign the word středa. For some reason, I can't say that one. Too many consonants in a row.