The truth is that there is no trick to slot machines. They provide random results based on set mechanics and it all comes down to luck. With that being said, not all games are the same, so picking the right options is key, and you can still change the size of the bet throughout the session for better results.
In general, it's best to pick the machines with the highest payouts. Search online to find specific machines that are known to have a high RTP ( return to player ). Pay attention to volatility, too. Low volatility slots have a higher chance of winning, but high volatility machines usually offer a bigger payout.