Much like any online game in the world Lag in League of Legends is an everyday occurence. Usually its just random hiccups here and there. But for some the lag is actually game breaking.
Now there is no definite way to lower ping in LoL as the lag can be due to multiple things and so you have to try several things to see what does and doesn't work. And that's a good thing, because in many cases doing slight tweaks is enough to solve the ping related issues in LoL.
You can break the problems down to two broad categories;
1. Local issues
2. Network based issues
You can read about all the problems and their fixes in this simple https://www.killping.com/blog/how-to-get-lower-ping-in-league-of-legends/.
Hope it helps you out