Here is a short list of stuff you can do today for the environment

1. Support organisations that helps the environment

This, we as individuals can't make all changes needed by ourself, but as a community we can make a large impact and inspire other to do the same. There is a lot of organisations you can check out, both political and non-political organisations. You can both contribute by giving money or by offering your labor in different projects. Here on Hive we have a project called @Cleanplanet which aims to support people who devote their time to going outside and clean their community. Such a great initiative and this is somthing I'm going to start doing, since I wanna lead by example, instead of forcing changes upon people.
Other easy changes you can do are to switch search-enginges to Ecosia, which plants trees for the money they make, or to Oceanhero, which are donating it's money to projects aiming to clean up our oceans.
There are tons of other organiations aswell, but it's all up to you to choose which you want to support.

2. Lead by example - Take the bike whenever possible

Lead by example is maybe the biggest thing anyone of us can do, it's hard to be the people in the front-line but someone has to take the lead. There are many ways on person can lead by example. Great Thunberg is leading in her way, which maybe all people don't support, and that's the great part that you don't have to do the same. One great example is that you can start to take the bike instead of the car everytime you need to go somewhere. You can switch out the plastic bags to some textile one's which can be used many more time. You can switch you diet to a vegeterian or vegan one.

3. Recycle - Contribute to the circular economy

Where I live this is already a pretty established thing that most people do. We sort out the glas in one container, metal in another and the left-over foods is being transformed to compost.
This is a curcial step in order to change our economy to a more circular one.

4. Save electricty - Small changes at home can make a big difference

Change you lightbulbs to LED will both help you spend less money on that electric bill and help the environment at the same time. Turn of the computers each time you go to bed, the stand-by function actully draws electricity. And also always turn of the lights when your not in a room, sounds so basic but every thing helps.

5. Eat local food

Instead of eating foods that have traveled around the entire globe to reach you plate, eat local foods and at the same time support the local economy. We need to be more concious about how much impact the food is having on the environment. Eat more seasonal foods, eat less meats and make the food yourself instead of buying semi-finished foods.