You have got the idea that they used to get losses cause they don't know to analysis the stock, they never do find that how business/company Fundamentally(actually) work and at last end up with losses.
So, For you to not make that silly and immature mistakes, let just know that How you can do Fundamental analysis like an expert.
If you don't know to Read balance sheet or financials then you should not invest in stock market on your own(Instead invest in mutual fund, PMS, etc.)
There are many ways to do Fundamental(company) analysis but I would just explain most effective and important things in simple and short about this which useful for individual:
1. Quality of product and services: The most important factor for long term growth investing for any company is to have a good quality of service/products to the individual customers of company.
Example: Apple have not most sells in phone industry but still it get more revenue than any other smartphone companies cause it's quality is great so, it's demand and price is high along with good services to customers.
2. Management service: In this factor you should have known that the management is serving/working well, so to know that all you need is to know they are keeping there words and plan or not, like they have done their projects or plan till the time according to them and you can check accord to historical data.
Also It should be good that CEO or Owners would have high share of company as they could implement any decision/plan without anyone's opinion or restriction.
3. Financially strong: Here, you need to have knowledge of finance to determine the financials are good or not but individually certain knowledge that enough to read and understand the Balance sheet are enough for invest in stocks or business.
Some signs to identifies the good stock financially are(for long term):
1. The P/E ratio less than 15 is a good but it should not be negative.(Remember it's just signs, you need to your own analysis).
2. Debt should be less than 40% of company or else, it could become burden to company in future although it's my own experience
3. Liability should never not be higher than Assets of the company
4. The profit should increasing since at least 2 or 3 years .
5. Last but one of the main point is that the valuation of company should not be so high or overpriced.
Comment any concern and doubts.
Please don't abuse and don't use violent speaking