It is absolutely imperative that you read the poem through first at least twice. I would suggest that you whisper it to yourself, even in exams, because poetry is a highly experiential literary form and this allows you to really get a feel of what the poet is trying to convey. It also helps a great deal with locating literary techniques such as sybillance and plosive sounds. Next it is key to go through and annotate the poem so that you have a line-by-line breakdown of the techniques used. This makes your life a lot easier when it comes to writing the essay.
I cannot stress enough how important it can then be to plan your essay - it can be really dull to hear it said over and over again by teachers, but realising the importance of planning drastically raised my grades as time went by. I would write the question at the top of the page and think to yourself "what are they actually asking me?" because then you focus on the key words in the title themselves rather than your take on what it means. You want to remain as focussed on the question as you possibly can in your essays and this will really help you do so.
If the question were 'Explore how Seamus Heaney present attitudes towards a parent in ‘Follower'.' Then the necessity for realising the title's key words becomes apparent. The key notion to explore is attitudes towards parents, not exploring parents themselves. It seems petty, but it can affect the relevance of your essay dramatically and lose you marks if you make incorrect assumptions about what the question is asking.
The next step that really helped me was to locate a line of argument; a preliminary gut reaction to the question. Using the previous example this might be as simple as "Heaney juxtaposes a childish sense of admiration and adoration at the poem's beginning with an adult sense of frustration by the end". This is purely as a personal guide for you such that when you are writing your essay you can check back and think 'does my argument correlate with my initial line of argument?'. This should really help you to present an argument that the marker can follow with ease - a sure way to maximise your AO1 writer's craft mark.
Next in the planning stage comes separating the paragraphs you intend to write. You could do this in the given example as 'admiration', 'adoration' and 'frustration'. Then pick lines, clauses and key words that endorse these attitudes towards parents. You can then draw on your intitial annotations when you start to write to really secure the marks for AO2 following the classic formula: Point, Evidence, Analysis. The analysis should really focus on techniques that back up your intitial point and should be relevant to the quote you used as evidence. This is also the time in which you can cite relevant AO3 and AO4 so drawing comparisons to other texts if faced with a question that asks you to do that and including context from the time that may justify an attitude you have analysed. These are very important to gain the top marks and should not be neglected.
Introduction and conclusion can be down to personal preference. I would stress that the first line should really grab the reader's attention; waffle is useless to a marker who is reading their twentieth essay of the day. Grab their attention! Then lay out what you are going to argue and signpost your paragraphs eg: 'Examination of the poem's initial sense of adoration and admiration, juxtaposed with the frustration present at the poem's conclusion should effectively illuminate how Heaney presents attitudes to parentsin this poem'. You would then write paragraphs 1, 2 and 3 on adoration, admiration and frustration respectively.
The conclusion should not recap the essay. The person has just read it! Instead you should be looking to close out the essay concisely and reiterate the argument itself, not the points. To do this I would bring in one further point that you haven't made in the essay.
Using this structured approach to my English studies really helped me to go from really quite disappointing marks to the top grades. Try and make your argument as clear as you can to the person marking your essay and the marks will come; people want you to do well!