Some exercises for the "th" sounds for a foreign learner

Question

What is the right technique for acquiring the "th" sounds? Are there any really proved useful exercises or tongue twisters which can help to get them?

I think after some training I've managed to pronounce both th sounds (voiced and unvoiced) correctly. But the problem is, I can't pronounce a clear decent th sound after some characters, like t, s, z, d, in a sentence without a pause or a little contortion. The goal is to use it freely in speech, which I'm definitely not able to achieve right now. I tried various exercises, like tongue twisters or just repeating some hard for me collocations, but nothing seems to cause a great improvement (or at least any).

My native language is Russian if it could help.

A few examples (the hard places are emphasized as code):

• it's the best thing in the world.
• and there are many..
• let them..

P.S. I've found a related question about pronouncing "th" sounds, but the question was about children with English as the first language. My question is intended for a grown-up foreign learner.

Answer 1

As @snailplane has noticed, practicing is the key.
Let me share more considerations a language learner may find useful during practicing:

1. Mind the contrast between "s", "z" versus "th"; Practice words in pairs (sink-think);
2. Pay special attention to pronouncing the contractions (it's the);
3. Don't depend solely on a sound. Take a native speaker and ask them to show how their tongue moves, what is the correct position against teeth, etc. There are many videos on the Web, with extreme close-up footage, like this video on YouTube;
4. Find a list of tongue-twisters like "Cathy's twenty-seventh birthday is Thursday, December the third" from the video above or from here and practice them;

Answer 2

Native speakers find it difficult, too, and that is why we don’t pronounce those three examples as you might expect us to. Most of the time they occur as

Iss the bes thing in the world

an there are many

Le' [glottal stop] them

Answer 3

Another note on pronunciation: I find that when the "th" sound comes after "t", "d", or "n", this preceding sound is dentalized: instead of putting the tip of my tongue behind my teeth, as I normally would to pronounce these consonants, I put the tip of my tongue on my teeth. The result is that my tongue doesn't have to travel as far in order to move into the "th" position, so I can say the phrases "in the world", "and there are", and "let them" much more quickly than I would be able to otherwise. (For "and there are", I do this with the "n" and the "d" of "and".)

The "s" sound can't be dentalized this way, because then it would become identical to "th".

Answer 4

Start by pronouncing v. Notice the friction between your top teeth and your lip. Continue pronouncing v, but replace the lip with your tongue. Your top teeth will continue creating that friction.