To learn to chant so that you are able to be properly behind the mantra needs practice. Mechanical chanting will effect but slowly so it's better to learn to chant so that you can produce effective sound waves which really create.
The components to proper chanting are: pronounciation, volume, rhythm and the ability to get the sound waves to vibrate.
Pronounciation you learn by chanting the way your Guru - Teacher teaches you. Nowadays it's easier because we have YouTube, SoundCloud for example from where we can listen and also chant along.
Volume can be from whisper to quite strong voice even inside chanting without voice coming out from your mouth is possible in your mind or from lower chackras. When you practice you can play with the volume.
The chanting rhythm can be slow keeping a short break between every mantra you chant. You can also chant the mantra shortly or lengthen certain syllables of it. By practice you learn to do it effortlessly.
The vibrational effect comes as a result from the three first elements and when you are behind your chanting from the bottom of your spine up to the top of your head. This means lot of practice but it's worth of it.
I have learned this by chanting a lot and from a certain point every mantra has began to teach me - mantras have initiated me and are still teaching. Lot of I have learned from Dr. Pillai - Babaji. The connection to Him is very strong and have learned a lot from his Online Programs.
Tip of the day: Play with mantra when you are able and when comes times you feel hard to chant don't give up but find effortless chanting or break the barriers with short but effective chanting. Even listening the mantra can help you.
I have created a course where I teach how to chant OM mantra from the beginning to use it as a tool of creation: