The phoneme /ʌ/ is sometimes tricky for ESL students. I call it the caveman phoneme because it strikes me as a sound early man could have made when he emerged from the caves and began uttering his first words. It's a lazy sound, requiring little effort and seeming to originate from below, as if from the belly. It's the sound native English speakers make when pausing to think about what they're going to say next.

There is no one letter to represent this sound, so it is often mispronounced by newcomers to the English language because they tend to focus too much on the written word instead of the sound. When learning new vocabulary in English, always focus more ​on the sound of the word rather than the way it is written. 

I've found that the smallest words present the most problems and are often overlooked. So let's begin with them. Note the various ways the words are spelled but phonetically still have the /ʌ/ sound.

Keep it simple! The best resources for studying English are those with audio tracks of native speakers reading a text. 

With a good dictionary like www.wordreference.com, this becomes an excellent exercise for learning English.