How to counter Garen
Let us take a look on how to beat Garen. We will look at champions who are strong against Garen and who are weak against Garen. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Top champion who counters Garen. You can already win in champion select with the right counters for Garen. If you want to know how to counter Garen then you need to take into account the best picks vs Garen and the worst picks vs Garen. This Garen counter data is based on matches played by Pros on patch 13.24 and previous ones. It is important to see whether Pros counter picked Garen or whether they played as Garen.
Champions used by Pros to counter pick Garen
Looking at the matches from Pros (see table Pros counter picked Garen) we can see that they picked 
Jax most often to counter pick Garen. The matchup Jax vs Garen occured 24 times. Garen has 16 wins and 8 losses in this matchup. Learn how to counter pick Jax to get another perspective on the data.
Lane outcome for Garen
When looking at Garen 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 Garen. The lane outcome of Garen consists of three outcomes: Win, Loss or Draw. Let's take a look of Garen 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 Garen.
Conclusion
Analyze the available data and learn how to beat Garen. To master Garen take also a look on Garen builds and runes for Garen. Good luck, Summoner!