Think of it as writing up an investigation into something such as an idea. An expository essay is a great tool to explore an idea, but remember that you must fill your essay with more than just notions, reasoning and considerations. Consider previous research that has been done, other studies, journals, and previous attempts at the idea or subject you are writing about.
Do your research first
If you are able, you should do your research before you even pick your topic. If you do this then you can pick your topic based on how much research you dig up. If there is a topic that simply has loads of research behind it, then you can pick that topic and your essay suddenly becomes a lot easier to write.
If you have already picked your topic, or it has been picked for you, then do your research first. Do it because you do not want to find out you are on the wrong track after you have started writing. You can also research into other essays that have been written on your topic. Do not copy them, but if they have some interesting points or useable references then there is no harm in doing a little harvesting–just make sure it isn’t obvious because you will not be the first student to have thought of pulling things from online essays.
Reference every slice of data you insert in your essay
If you want a good grade then all your data must be referenced. Your reasoning and logic must be justified but not referenced, but each piece of data, no matter how small, must be referenced if you want a passing grade. The source must be academically viable and reliable.
Make it clear what is opinion, reasoning and referenced fact
It is easy to fall into the trap of allowing opinion or reasoning to come across as fact. It may be done by association, by proximity, or even with a bad transition (or bad writing). You cannot allow an opinion or reasoning to come across as fact or your reader (and professor) will want to see a source for that fact. If the opinion or reasoning you add is from somebody else, then consider the source and its validity. Do not remember that no matter how many dead people have opinions the same as yours, there are probably just as many dead people that have an opposite opinion (in other words, do not rely on the opinions of others–even if it comes across as reasoning).
Your research method will come under scrutiny
The reader will make judgments about your research method. If the reader cannot poke holes in your logic, analysis, and so forth, then the reader will poke holes in your research method. This is why it is often a good idea to set aside some space to explain your research method and justify it. You can show that you tried to avoid a positive bias and that you really did research as many counter arguments as possible. You may also like to justify your references as you write your essay, such as explaining a little about the references’ work and background to show its validity.
Come up with the counter arguments your readers will think up
The counter arguments you come up with may appear to damage your case, but they are actually making it stronger. You are taking shots at your own work so that the reader doesn’t have to. You point out the possible weaknesses in your arguments so that you can show how they do not matter or how they are not weaknesses. It is far better for you to come up with counter arguments than to let your reader do it. If your reader thinks up a counter argument that you do not address then that person will not be convinced by your essay.
Argue down your counter arguments as thoroughly as possible
You have to argue down your counter arguments so that you reader cannot retreat behind them. If you are having trouble arguing them down successfully, then you may have picked the wrong side for your persuasive essay. If you brush over your counter arguments, then your reader may not be convinced and may still use your counter arguments as reasons “not” to be convinced by your essay.