When I say "wrong" people always mishear as "long". Pronouncing "r" and "l" correctly is always a big challenge for me. In Chinese we also have a syllable pronounced like "r" and a syllable pronounced like "l" and I can never pronounce them correctly. So how do I practice that in English?
Put simply, curl your tongue further back in your mouth.
An 'l' is voiced and articulated with the tip of the tongue aginst the ridge behind your top teeth. An 'r' is also voiced but the tip of the tongue is higer, and further back aginst the roof of your mouth.
If you begin with an long 'l' and move the tip of your tongue backwards along the roof of your mouth, the sound will turn into an 'r'.
Do not use your tongue at all. Keep it well out of the way. Put your teeth together, make a voiced sound, then move your teeth apart as your voicing continues. This makes the "R". From there, move straight into the "O" position, and continue with the rest of "wrong".
Edit: To pronounce an "L", place the front portion of your tongue flat against the roof of your mouth, so that the tip of the tongue is just behind your upper teeth. Make a voiced sound, then move your tongue downwards as the voicing continues.
Rah rah Rasputin Brought along a broad On the road to rot a lot. Plot to prod her to crack some pot With some reed and weed Bleat to greet her To agree to breed.
The 'L' sound should resonate with your throat.
The 'R' sound should resonate with the area between your tonsil and upper set of teeth.
Practice the verse above without making any L or R sounds, but
when you encounter an R vibrate your tonsil area and breathe the word out of your upper set of teeth and and try to feel the breathing flowing underneath your tongue.
When you encounter an L vibrate your throat and groan and try to feel your breath passing through the tip of your tongue.
Practice it frequently and then when you are used to it, gradually replace the tonsil vibration with R sound and groaning/throat vibrations with L sound.