Yeah, like others have said, you can easily cancel during the free trial, which I've personally done. I've also had a subscription for a while, and renew it every so often whenever I'm in the mood to dig around again. There's all sorts of things you'll be able to look up for free, but as you probably know, some of the searches are limited unless you get that premium membership. One of the advantages of that particular site is that there's a chance other members have posted photos or other interesting media of your ancestors, which you should at least be able to see thumbnails of. I was able to see thumbnails of my grandfather as a child, and was able to grab the full version of the photo once I got my premium membership.
Findagrave often has a lot of great information in addition to just the photos of the graves, you can often find photos of the people themselves, obituaries, sometimes even stories and articles, depending on what people have added. You can also request people to look up someone's grave and take a photo of it for you; something I've done for some of my relatives out of state.
Oh, and Google is totally your friend.
I can't tell you how much information I've found on my family history thanks to the various sites I've found through searches. For example, I found a neat story of how my great-great grandfather, who fought in the civil war, switched places with his twin brother while enlisted in order to visit his sister. No one suspected the switch! Which meant my great-great uncle was technically in and out of the Union Army in just a few hours.
Anyway, I've been able to track parts of my family back several hundreds of years. It's pretty fascinating stuff and gets quite addicting!