It is easy to find students making mistakes with footnotes as a lot of students use footnotes without actually knowing how they should be used precisely. The thumb rule says that if you do not know the way in which the footnotes should be used, then you perhaps should not use them at all.
First of all let us understand the distinction between footnotes and bibliography. The purpose of using footnotes is to provide the reader with some extra information about the content. As the name is indicative, a footnote is to be found at the bottom of the page and gets it referencing through a superscript number placed on the main content. While, the bibliography page is the last page of the section of your essay or dissertation and incorporates the entire citation information for any of the information that has been used in the content and retrieved from any external source. The purpose of bibliography is to give the complete detail to the reader including the place and time of publication of the content in reference. All these details are not included in the footnote.
There is a way to use the footnotes correctly and one should actually be very specific about adopting the correct means. Always write your footnotes in the last. Most of the times it is the shortest version of the citation placed in the bibliography. The best thing to do is to leave writing the footnotes till the end until the essay is finished and the entire bibliography is complete. Never think that using footnotes can be a replacement for bibliography. The impact of bibliography may diminish with a lot of use of footnotes, however it does not become redundant. A bibliography is a proof that you are a well-read writer, so all the information that you have adopted in your writing, whether it is directly referenced or no, bibliography is a place to tell about it.
Footnotes can be written in different citation styles and each university may have its own norm about which referencing style to follow. The most commonly used referencing styles are Harvard, Oxford and Chicago. Whichever be the preference of your university, focus on the intricacies that the style demands.
Footnotes isn’t a thing to be forgotten and how much ever you get trapped in the writing process, do not ignore the use of references and bibliography as that is the key distinction between generalised writing and academic writing.