Check that you know what the word limit is and whether there is any leeway (10% +/- for instance). Bear in mind that being seriously under is often as bad as being seriously over - both may indicate that you haven't answered the question that was set or haven't answered it adequately. Being late is only okay if you get permission from your tutor first. Allow time for postage or problems uploading. Work out your action plan - this might include reading additional material, visiting a library, checking data with other sources. Don't plan to do everything on Monday only to find the Reference Libarary is closed!
You may need to speak to a particular person only to find they are not available on Wednesdays. Your holidays, tutor holidays, Bank Holidays, any equipment you need being unavailable for any reason, children being on holiday which means you can't work, family visiting from Canada, etc. Using half the word count to restate a small point from different authors or references may not score many marks. Check the information you are using actually supports your claims! Though classics in their time the side of a cornflake's packet might not be the most credible reference source in an academic piece about technology. Even if it is credible check as much as possible. With few exceptions 'the bloke in the pub said......' is not likely to garner too many marks (If the bloke in the pub is Dr Russell Stannard and your TMA is about Physics you may be okay). How should it be presented and laid out? HTML? RTF? Word document? Hand carved on tablets of stone? Probably your name and PI, maybe the question restated, maybe a table of data, certainly references and citations, maybe a picture of someone or something Anything else that might help you support your work - If it's not specifically stated as "Not allowed" check with your tutor. Who knows a real elephant attached may be worth extra marks! Sometimes certain things are strictly not allowed - again you should check if you are in doubt. Unless the TMA specifies a different structure you should always include these components.
Remember the old adage that you should "Tell 'em what you are going to tell 'em, tell 'em and then tell 'em what you've told 'em" This is where you set the scene. Explain to your reader what you are going to discuss and how (this is particularly important if you are using a particular convention such as using a separate page for references).
Tell your audience what you intend to tell them! This is where you lay out your well reasoned arguments and support them with well selected evidence from credible sources. Courses that use HTML reports offer a great opportunity for using images to explain points and to 'lift' the layout. Unless specifically instructed not to you should always use them!
There are some superb images available on the web which can be worth thousands of words. Check that they actually work and take the reader where you say they go! There are few things more frustrating than being offered a link to the secret of life, the universe and everything only to find the link is broken or actually goes to an online Pizza Palace. Again for HTML reports - use colour wisely but use it. Take advantage of the medium. Plain old A4 paper doesn't offer these benefits but HTML does and many courses require that colour and tables are used to demonstrate that you have grasped the basics of the medium as well as the course content. Tell 'em what you've told 'em!
Bring together the strands of your argument and demonstrate how you have achieved the objectives you laid out for yourself in the intro. Again great work can be spoilt by needless typos or poor grammar. Proof read, see if someone else can check the grammar (not the content!), use a spell checker (with caution) but make sure you present your work as well as possible by looking at these details.