Amazing evidence sounds great, but what should I be looking for? You should be looking for credible evidence provided by credible sources, and that can include yourself if you've done relevant studies or experiments.
Awesome! So how do I know if a source is credible? That's easy! Just take a look at a few different criteria to see if any source is credible!
Something important to credibility is how recent something is. If a study was done 20 years ago, then it will be less useful than a study done just a year ago. Always aim for new and fresh examples for your arguments!
Another thing you need to keep in mind is both who is the author of what you're reading, and what is the point of their research? Not all people are entirely credible, and some people even get their credibility stripped from them after releasing biased or dangerous information. It is always important to background check the author of any study to find out who they are, and if their data may have some form of bias. It is also important to pay attention to the intent behind the words of the author. Was the author funded by a specific party? Are they an outspoken advocate of the topic of their study? All these things could lead to a bias that may be more hidden. Be careful!
Another important thing to keep in mind is to be incredibly careful when you're looking at sources you find on the internet. Sites like Wikipedia CAN hold useful information, but it can also be FILLED with misinformation on any given subject. The same goes for any other web page you find. Always check the credibility of your sources!
Don't forget to keep in mind your audience for any given debate. If your audience is expecting an academic argument you'll want to find some top of the line peer reviewed or academic studies, and avoid the more emotionally charged studies.
Another useful tip might be to check out newspapers or magazines. They aren't always reliable so remember to background check everything you plan to use, but both can be filled with valuable and recent information!
When in doubt, take to your local library for research assistance, or if that's out of the question, take to Google! There are a number of great sites that you can find online that host things like peer reviewed studies and other academic papers. Two good ones (That I have had personal success with) are EBSCO (https://www.ebsco.com/academic-libraries) and DOAJ (https://doaj.org/). Hope this helps!