Hey Eve, I hope Alex wonāt crucify me but this is the word-for-word question I kept asking myself when started my real investment account back in the days (in 2017 
) and I believe this is the one every individual should attempt to have some understanding of, so I am going to take this one.
Will start from afarā¦ I originally thought that books are not for me - I needed an easily digestible material in a form of short articles or forum posts. Although my first destination was Reddit (r/Investing + r/StockMarket + r/UKInvesting are very good ones to start with), I did not have the advantage of Freetrade community which by far seems to be the most fit-for-purpose place for beginners to obtain the knowledge and raise questions without risk of being patronised.
Albeit this is not quite related to researching a companyās financials, all of that information forms the overall awareness of how markets generally work, why do certain securities go up or down based on the news, why Utilities companies always rise when all other market sectors go down and vice versa - there are many other little things that all help a lot.
Now getting to the actual research. Whilst Freetrade have covered many aspects in the Do your own research! blog post you referred to, it is, of course, not possible to cover all aspects in one piece. In fact, it is also important to remember that any individual research (like yours and mine) outcome or assumption is probably something that big financial analytics agencies have already established before us. The only difference is that we make our research to understand which type of securities (aggregate name for stocks/shares/bonds/index funds/ETFs/etc.) appeal to us and our risk profile.
For example, you could easily avoid looking at companiesā earnings reports if you are happy with data that is one year old - perfectly fine if you plan to invest (buy and hold) rather than trade (transact while instantly reacting to all the news and press releases) and simply use Stock Screeners.
Stockrow is a very nice one, gives you circa 10 yearsā data - just try to type Amazon, for example. Once in, ignore the graph and look at the ratios below: Market Cap, Enterprise Value, Revenue and others. The beauty of it is when you hover your cursor, it will explain what each of these ratios represent and even tell you what is generally āriskyā or āacceptableā. For example, looking at Debt to Equity Ratio (since you mentioned debt already), it will say that the value of āless than 1ā is considered as a low level of debt, whereas 2 or more - high. Whilst Amazonās is only 0.70, Teslaās, for example, is shocking 3.77!
Once you get your head around the ratios, you will realise that if the key ones like P/E, P/B and P/S are positive - most of others will be positive too, meaning good fundamentals.
The next step is trends, which is represented by fancy graphs below the ratios. Constantly rising revenues since 2008 - absolutely great. See many green dots on the graphs? Marvellous! Assets rising faster than debt levels? That is what we need. And all other ones you could look in a similar fashion. Certainly not all of them will be perfect, but it is vital to have key ones in āgreenā, which are the revenues, the profits and the debts rising slower than the earnings.
Now, the last part is the nature of the business, its long-terms aim and overall purpose. This one is qualitative and cannot be established using numbers only. For example, our Amazon is notorious for its constant growth - they do not pay dividends, they do not make profit - all they are aiming towards is growing and penetrating into other sectors (Healthcare, Shipping, Banking), hence you see their Revenue (the first line) growing 20% every year, and now it is 10 times more than 10 years ago. Therefore, you could immediately discount the importance of P/E (Price to Earnings ratio), because it would contradict the idea of growth. But how would a beginner investor know that? By going back to Step 1 - Reddit, articles, journals, news, Freetrade community - all of these, to some extent, will enhance your knowledge and awareness. Whilst I have only been interested (and have been researching) in markets and investing for a year, I can absolutely see its importance and the abundance of further knowledge that can be acquired going forward. It is a fascinating world, it becomes extremely more interesting once Step 1 is crossed so I absolutely advise everyone to start researching these things at the earliest possible stage.