You can look on the internet for interesting things to do and on Youtube for ideas. There is also couchsurfing
There is also the philosophy of not planning anything because that's when everything happens!
Here is an example from Taiwan in 2017
I had arrived the day before in Taichung and I had no plan when I woke up that Friday morning.
At the last moment, I find a CS accommodation for the same evening and am invited by another CS host for a cooking lesson at 7pm on Saturday with her children and her neighbors. They also tell me "Well, on Sunday we're going to accompany our son to Lukang for a rollerblading competition and then we're going to visit the city, do you want to join us?"
That's it, a very busy weekend even though I hadn't planned anything