In this Kali yuga, age of quarrel and hypocrisy we all have shortness of memory. Therefore if you want to memorize what you have read in the Bhagavad-gita, you will have to work very hard. To begin your Bhagavad-gita memorization program you should solidly learn this verse, which is the key verse of the Bhagavad-gita, both in Sanskrit and English:
mām ekaṁ śaraṇaṁ vraja
ahaṁ tvāṁ sarva-pāpebhyo
mokṣayiṣyāmi mā śucaḥ
"Abandon all varieties of religion and just surrender unto Me. I shall deliver you from all sinful reactions. Do not fear."
Read this verse aloud many times. Then without looking try to repeat it. Check to see how well you did. Then read it aloud again many times. Again try to say it without looking. Repeat this pattern again and again until you can say the entire verse correctly without looking. Do this both for the English and the Sanskrit. And then every day in the early morning test yourself on the verse. Try to say it without looking and see if you got it right. Every morning you must recite it in both Sanskrit and English without looking. You should only look at it to double check that you are getting it right. You should also memorize the chapter number and verse number. In this way if you will drill this verse until you memorize it and continue drilling to retain it, this verse will become as familiar to you as your own name, and you will be able to call upon it at will in all times and places to strengthen your own Krishna consciousness and to authoritatively enlighten others in the science of bhakti. Once this verse is very solid, you should add more and more verses to your repertoire in the same manner as you learned this one.
The principle here is throwing the mud against the wall again and again and again until finally some of it sticks. In other words, if you drill your brain enough it will become trained to be able nicely retain the scriptures. The more you learn verses, the easier it will get. You should have a lifetime goal of mastering at least 108 verses.
So now get to work and enter into an exciting new chapter of your life.
Sankarshan Das Adhikari