Where should a person who wants to start memorising the Holy Qur’an begin?

Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have
mercy on him) was asked this question and he replied as follows: 

What we advise him to do is to begin with al-Baqarah, unless
he has memorised from al-Mufassal [the soorahs beginning with Qaaf, until
the end of the Qur’an – al-Haafiz Ibn Hajar], because for some people it is
easier to memorise from al-Mufassal because the soorahs and verses are
shorter, and they hear them a great deal from the imams in the mosques. So
if that is easier for him, let him begin with that which is easier. We also
advise him to pay more attention to what he has already memorised than
paying attention to memorising a great deal, because paying attention to
what is already there takes precedence over paying attention to what is not
there.