First you have to know what you're using the quote for. If you're using it to back up a technique, then you have to make sure that the quote you're memorising has the technique you want in it.
The main thing is to know what you you are going to write about about a certain text. Let's say you're doing Text A. You know that if you're going to talk about Text A in the extended response, you will only talk about three certain techniques and their effects. You would then find the quotes to back up those techniques and memorise those quotes only.
Alternatively, you can memorise the entire poem.