How to start investing: 6 costly mistakes to avoid

Christopher Ruane shares six mistakes he would try to avoid if he had the chance to start investing for the first time again.

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

As an investor I’ve made my fair share of mistakes — and learned from them. If I was to start investing today, here are six potentially costly mistakes I’d try to avoid making.

1. Not diversifying

No matter how great a company is, it should only ever be one part of a portfolio. A balanced, diversified portfolio is a simple but important form of risk management. It’s tempting to start investing by putting most or all of one’s funds into a single company. A lot of employees do this if they receive shares through an employer share scheme. No matter how good the results can be in any one situation, this is a high-risk strategy I would never use.

2. Over-emphasising management

There’s no doubt good management can boost a company’s performance. But if the only competitive advantage a business has is its management, that’s a risk. I always look for additional sources of competitive advantage, such as proprietary processes, strong brands, or entrenched distribution networks.

This is one potential mistake I’m bearing in mind when it comes to my position in S4 Capital. Its founder, Sir Martin Sorrell, is clearly talented. But it’s the team and ecosystem he is building around him that makes S4 investible for me, not just Sorrell’s involvement.

3. Focussing too much on history

Most investors who start investing look at a share’s historical data as it can be highly informative. What have its earnings been? Did its revenues grow? What is the historical dividend yield?

This is all useful information – but not in isolation. Past performance is not necessarily a guide to what will happen in the future. So I think it’s a mistake to focus too much on past performance rather than considering both historical performance and, more importantly, future outlook. It was that mistake that led me to purchase Shell only then to see it cut its dividend for the first time since the Second World War.

4. Not seeking alternative investment views 

If I have a theory on a share, I’ll try and find out what other investors think about it too. It’s tempting to pay more attention to views which match mine and overlook opposing ones. It’s what behavioural psychologists call a ‘confirmation bias.

Every transaction on the stock exchange requires both a buyer and a seller. So it’s a mistake not to evaluate a share choice in terms of what could drive it down, as well as what could push it up.

5. Focussing on price not value

As investor Warren Buffett succinctly puts it, “price is what you pay, value is what you get”. In other words, a cheap share price doesn’t necessarily equate to a bargain – the share can still fall. It’s exactly that muddled thinking on price that led me to buy Centrica and my position remains underwater.

Instead, Buffett looks for high quality companies selling at what he regards as a fair price.

6. Trading too much

Trading has costs – financial, time, and sometimes emotional.

As a new investor, it’s tempting to jump in and out of positions in the excitement of stock trading. That is closer to speculation than investment. Many academic studies suggest that successful investors trade fairly infrequently. They prefer to select great stocks with fabulous long-term prospects then let time hopefully work its magic.

Christopher Ruane owns shares in Centrica and S4 Capital. The Motley Fool UK has no position in any of the shares mentioned. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

Burst your bubble thumbtack and balloon background
Investing Articles

£15,000 invested in Helium One shares in December 2020 is now worth…

James Beard explains why loyal Helium One shareholders will be hoping the group can soon commercialise gas production.

Read more »

Departure & Arrival sign, representing selling and buying in a portfolio
Investing Articles

£1,000 now buys 264 shares in British Airways owner IAG. Worth it?

This time last week, IAG shares were flying high. However, in the blink of an eye, they’ve fallen about 16%.…

Read more »

Finger clicking a button marked 'Buy' on a keyboard
Investing Articles

A once-in-a-decade opportunity to buy BAE Systems shares ‘cheaply’?

BAE Systems shares are on the charge. Ken Hall investigates if this could be just the beginning for the FTSE…

Read more »

Santa Clara offices of NVIDIA
Investing Articles

A once-in-a-decade chance to buy Nvidia stock on a P/E ratio of less than 20?

The last time Nvidia stock had a sub-20 P/E ratio was over 10 years ago. Could we be looking at…

Read more »

Finger clicking a button marked 'Buy' on a keyboard
Investing Articles

How did the FTSE 100 near 11,000 so quickly?

The FTSE 100 has been storming higher in 2026. What are the reasons for the surge? And could it continue…

Read more »

Cargo containers with European Union and British flags reflecting Brexit and restrictions in export and import
Investing Articles

£1,000 buys 219 shares of this red-hot UK industrial stock that’s outperforming Rolls-Royce

Rolls-Royce shares have been a very popular investment in recent years. However, over the last 12 months, this under-the-radar stock…

Read more »

A tram in Manchester's city centre
Investing Articles

Here are 5 things Greggs shareholders just learned

Ben McPoland takes a look at some key bits from Greggs' 2025 report. But with consumer spending still under the…

Read more »

Businessman with tablet, waiting at the train station platform
Investing Articles

Lloyds’ share price has plunged 14% from its highs! Time to buy?

Lloyds' share price is back below 100p amid sinking market confidence. Should investors consider buying the FTSE 100 bank as…

Read more »