How to counter Tristana
Let us take a look on how to beat Tristana. We will look at champions who are strong against Tristana and who are weak against Tristana. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Adc champion who counters Tristana. You can already win in champion select with the right counters for Tristana. If you want to know how to counter Tristana then you need to take into account the best picks vs Tristana and the worst picks vs Tristana. This Tristana counter data is based on matches played by Pros on patch 15.3 and previous ones. It is important to see whether Pros counter picked Tristana or whether they played as Tristana.
Champions used by Pros to counter pick Tristana
Looking at the matches from Pros (see table Pros counter picked Tristana) we can see that they picked 
Ezreal most often to counter pick Tristana. The matchup Ezreal vs Tristana occured 25 times. Tristana has 13 wins and 12 losses in this matchup. Learn how to counter pick Ezreal to get another perspective on the data.
Lane outcome for Tristana
When looking at Tristana counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Tristana. The lane outcome of Tristana consists of three outcomes: Win, Loss or Draw. Let's take a look of Tristana lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Tristana.
Conclusion
Analyze the available data and learn how to beat Tristana. To master Tristana take also a look on Tristana builds and runes for Tristana. Good luck, Summoner!