Here are some "rules of thumb" we often tell students. They aren't rules, but rather some guidance to give you an idea of what might be expected of you
How many references should I have in my assignment?
There is no straight answer to this, it depends on what you're writing and what your lecturer expects, but you may want to consider having a minimum of 8 references for a first year assignment and grow from there.
How many references for a paragraph?
You always need to have at least one reference for any fact or concept that was not your own work. But probably no more than 3 if possible, so pick your best sources. Depending on how many sources of information you have used, you may only have one citation for that paragraph, or you may have several.
If you have written a paragraph that did not use any information or ideas sourced from another work, you do not need to include a citation - but you should consider what the purpose of the paragraph and your assignment is, and whether you should include research. Remember, your lecturer is not looking for your opinion, but rather your informed opinion. If you are writing a reflective paragraph that only involves your thoughts and opinions check with your lecturer to see if they want you to include sources to back up your ideas.
Depending on your genre and your subject area, your introduction and conclusion may not contain facts or information taken from an outside source (only an outline of the concepts you will discuss/have been discussing), in which case you do not include citations in your introduction and conclusion. However, if you have included information that has come from a source in these paragraphs, you must include a citation.
Do I have to keep putting in citations in if I'm using the same person for the whole paragraph?
You have to make it clear where each bit of information came from, but you don't always have to keep using full in-text citations every time if you are only talking about one source.
If you include the name of the author at the start of the paragraph and put the year in brackets after it, you do not need to keep including the year every time you refer to the same work within that paragraph as long as (and this is the important bit) you keep making it clear where the information came from. Include a full in-text citation at the end of the paragraph.
Example (using APA style)
Among epidemiological samples, Wagtail (2020) found that early onset social anxiety disorder results in a more potent and severe course. Wagtail also found …. It can also be seen in Wagtail’s study that … Wagtail confirmed that ... The study also showed that there was a high rate of cat related incidents (Wagtail, 2020).