I know this may sound obvious and patronsing but before you read the poem READ the question!!! This will give you the focus of the poem so you have an idea before you start to read the poem. Also if you don't understand parts of the poem DON'T WORRY - examiners mark positively so they give you marks for what you wrote, you don't lose marks for parts of the poem you missed. If you don't understand something DON'T make things up!! Also try some practice questions and get your teacher to mark them.
I hope this helps and if you need any other help I'm always happy to help out if I can :)