The letter Ё [yo] has birthday – 29 November, 1783. It is over 200 years old. It is the only letter that has appeared in the Russian language much later than others and has non-binding status in writing. This letter was introduced into the Russian language by Nikolay Karamzin in order to combine the letters "ie". The idea however might belong to princess Yekaterina Dashkova – there is no exact information. This letter has as supporters as opponents. Some people say it is a tribute to traditions and we should write this letter. Other claim that it just uses up paint in a printing-house and it is inconvenient to type this letter when printing on the keyboard. But no one has come to an agreement. The letter Ё [yo] is still optional in writing and still exists. It even has a monument in city Ulyanovsk. The letter Ё [yo] is very similar to the letter Е [ye] in writing but extremely different in pronunciation. But if you say the letter E [ye] instead of Ё [yo] – don't worry, it means you speak the Russian language used in churches [сёстры, сестры / s'ostry, s'estry]. But there are some words where the letter Ё [yo] is necessary: всё здесь – все здесь [vsyo sdes' – vs'e sd'es'] (everything is here – everyone is here) – the meaning differs. It means you should memorize the words всё [vs'yo] and все [vs'e].
So how to pronounce the letter Ё [yo]? At first it is pronounced like the letter Й [y] and then like О [o]. If we smile during the pronunciation of the letter E [ye], here we just stretch our lips for pronouncing Й [y], then make them protruded for O [o]. So in case we understand how to pronounce this letter, how should we read it if it has an informal status? The trouble is that most authors do not think fit to write Ё [yo] because everyone remembers where it sounds. But it is not good for Russian language learners. That is why you should memorize where it sounds to begin with common words like: жёлтый ёж шёл к ёлке [zholtyj yosh shol k yolke] (a yellow hedgehog went to the firtree). Apart from memorizing you should choose the textbook in the Russian language, which has texts with the printed letter Ё [yo]. That will help you to memorize such words without any fears during reading, so you will know whether to choose the letter E [ye] or Ё [yo]. And certainly the most important thing is a practice – speak and speak. You can also ask a teacher for help to make pronunciation an easy task.