Investment approaches and processes are often very simple, it is the execution and sticking to your plan that’s the hard bit. - Matthew Vaight

Matthew Vaight worked as a Fund Manager at M&G until he retired at 42. He kindly shares some of the multidisciplinary lessons that he learned during his career.
Poor Charlie’s Almanack is a collection of speeches and articles but is still by far the best introduction to multidisciplinary thinking in investing, plus a biting criticism of many professional investors in terms of their capability and incentives.
The Most Important Thing: Uncommon Sense for the Thoughtful Investor by Howard Marks, a pretty short book but packed with wisdom about how to invest…and how to think about investing. His client memos are worth seeking out too.
Often my default recommendation to completely new investors is a bit of a cheat but it is to read a handful of the Little Books that deal with investing:
The authors are all seasoned investors and their short books show that investment approaches and processes are often very simple, it is the execution and sticking to your plan that’s the hard bit.
Being a professional investor is essentially being a professional decision-maker with a very measurable outcome (as long as you give a margin for luck!), so I think there are huge learnings on how to make good decisions. Some examples that spring to mind are :
Completely ignoring the above answer…not having a clue what you are doing, shifting about depending on noise and the markets, buying things you don’t understand.
For instance, when buying a share you really are buying a tiny percentage of a company, you are a part-owner in that business and so you need to think like that…focus five years out, look at the fundamentals and competitive advantages of that business, see what cash flows that company can produce and so what it might be worth in a decade’s time, buy more if the market is giving you opportunity to buy at a significant discount to that value.
Don’t buy things just because you think they are going up! Or because a mate/cab driver gave you a tip!
They can simplify down to the things that really matter, have the clarity of thought to make the big decisions when required, see shifts in the big drivers of investment markets, and are emotionally retarded enough to stick with those decisions when times are tough.
I used a software program called HOLT that helped me screen the market, make comparisons easily across geographies and sectors, and identify mis-valuation opportunities. However I did probably become overly reliant on it, plus it had flaws that made me miss opportunities or sell too early.
So instead I’d say a local coffee shop with a friend/colleague…and before each decision, you have to go have a coffee before you press the button (that break is invaluable), and justify your decision to the other person. It might just stop you making a stupid decision…or make you double up and go all in!