Start with understanding what the company actually does. Read their annual reports, especially the business description section. Look at revenue trends over 3-5 years rather than quarterly fluctuations. Focus on companies whose business models you can explain to a friend. Many successful investors started this way - Warren Buffett famously avoided tech stocks for years because he didn't understand the business models.

Following hot tips without understanding the underlying business. In Thailand's market, we often see people chase stocks based on social media recommendations or broker calls without doing basic research. The most costly mistakes happen when investors put significant money into companies they can't explain. Always start with small positions while you're learning, and never invest more than you can afford to lose in individual stocks.

For most individual investors, 15-25 stocks across different sectors provides adequate diversification without becoming unmanageable. In the Thai market, avoid putting more than 5% in any single stock initially. Consider geographic diversification too - maybe 60-70% Thai stocks, with the remainder in regional or global markets through ETFs. The key is balancing risk reduction with your ability to actually monitor your holdings.

Sell when the original investment thesis no longer holds true, not because the price dropped. If you bought a stock because of its market position and that position deteriorates permanently, that's a reason to sell. Price declines alone aren't reasons to sell if the business fundamentals remain strong. Set a maximum loss threshold before you buy - many investors use 20-25% as a stop-loss guide, but the business health should be your primary consideration.

Technical indicators work better in liquid, heavily traded stocks. For smaller Thai stocks with low trading volume, technical analysis becomes less reliable because a few large trades can distort the patterns. Moving averages and support/resistance levels tend to be more useful than complex oscillators. Remember that technical analysis helps with timing, but fundamental analysis tells you what to buy. Use both together rather than relying on either approach exclusively.

Currency movements add another layer of risk and opportunity to international investments. If the baht strengthens against the dollar, your US stock returns get reduced when converted back to baht. Conversely, a weaker baht boosts foreign investment returns. For long-term investors, currency fluctuations tend to average out over time, but they can create significant short-term volatility. Consider currency-hedged funds if you want international exposure without currency risk.