There are two common issues with TMA writing. The first, referencing, has been dealt with here before. The second is "how the hell do I write an introduction/conclusion?"
Now, the introduction and conclusion of your TMA bookend it. They demonstrate that you know what you're going to write, and that you can summarise what you've written about at the end. And they are vital, because most essay TMAs take them into account in the marking scheme.
So, how do you write them?
Well, first off, you don't have to write the introduction when you start, and the conclusion when you finish. I often write the conclusion first, before I write anything else. I may well totally rewrite it before submission, but it focuses my mind on what the final result should be. Conversely, I often write the introduction last, when I know what I've written about. You don't have to write your essay in order at all - I'll often write a few sentences that I want to get in, but I'm not sure where, and then ease them in at the end. Or not, if they turn out to be unnecessary. The important thing is to START writing.
It's times like this that an essay plan helps. I SCORNED essay plans when I started my degree. "I don't need them, they're a waste of time", I thought. But with time, I've come to value them, both as a template, and as a working frame of reference. If you have a vague idea of what you're going to write about, and in what order, before you start, half your problems of arranging the content in your head and on the page are solved. If you can work out how much of your word count you need to give to each segment, then you have an idea of how long each part needs to be.
An introduction and conclusion should not take up more than 20% total of your word count. With a thousand word essay, try and get your introduction and conclusion at around 100 words each. Any more, and you're probably waffling.
So, introductions. I tend to be pretty explicit in my introductions about what I'm going to write, and allude to the TMA title. For example (and I'm making this up as I go along, so I really hope it's not actually a TMA title), if your title is "Discuss Cordelia's motivation and actions in Act One of King Lear", then you need to mention in your introduction that your essay is about Cordelia's motivation and actions in Act 1 of King Lear. This may sound REALLY OBVIOUS, but you don't need to be Shakespeare to write an introduction.
"In the play King Lear, Cordelia is a central character. She is the youngest daughter of the eponymous king, and in the first Act appears only once, and greatly displeases her father. This essay will examine her actions, and discuss the motivation behind them."
And that's it. In under 50 words, Cordelia is introduced, and the reason for writing the essay is explained.
Conclusions are equally simple. You have, hopefully, done what you said you were going to do in the introduction and written an essay discussing the motivation and actions of Cordelia in King Lear, or whatever your essay title was. Now, you need to sum up your findings and signal this is the end of the essay.
"To conclude, Cordelia's love for her father is unsullied by greed, and Lear is unable to accept the simplicity of it, as he is so used to abundant, false praise. In trying to be honest, Cordelia is disinherited by her father, but her honesty wins her the King of France as a husband."
And again, in 50ish words, the essay is rounded off neatly. All a conclusion does is state, briefly what you've written.
(I'm not an English Lit student, can you tell?)
So, don't fret about intros and conclusions. Fret instead about your essay argument, whether you're meeting the guidance (because if the guidance says read X, you better read X, and reference it, and quote from it if necessary), and whether or not you'll ever finish the horrible thing.