Before you hand in any piece of work, it's a really good idea to check it over for any mistakes, or anything that you want to add, remove or change. This is called 'proofreading'. If you can, leave some time, ideally overnight, between when you finish writing and when you proofread your work. This makes it much easier to spot any mistakes. However, you also need to make sure that you leave yourself enough time to make any changes that you spot!
When you proofread, keep an eye out for any mistakes you've made in spelling, grammar or punctuation. If you spot the same mistake more than once in your work, make a note of it so you can remember to look for that mistake in the future. If you are writing on a computer, you could use the 'find' tool to search for every time you've made the mistake.
Most word processing software will have features that check spelling and grammar, and highlight any mistakes. These can be really useful, but make sure you do your own checks as well. In built spell checkers will not highlight words that are spelled correctly but don't work in the sentence, for example 'wood' rather than 'would'. You will only pick up these kind of mistakes by reading the document yourself.
You can also use proofreading to check for the other things that are covered in this guide:
Have you answered the question that you were asked? Did you follow the instructions you were given?
Does your writing follow a logical structure? Does it make sense in the order you have written it?
If you are writing an essay or making an argument, does each paragraph contain one point? Have you provided evidence, and explained how the evidence proves the point?
One way of proofreading is to make a checklist of all the things you want to look out for, then tick them off as you go.