Visual research
Google images
personal examples
personal experience

It took me a while to add this to the list, but this is definitely one of my most used research methods ever. I use this for work (illustrating for a friend of mine) and a lot for Ces' classes. I think in images and vibes of how I want a certain scene to look like. Before I start creating I need more information to hold on to, I need a clear image. To achieve that I often go to Google and type in whatever has to do with the subject I want to work on. I screenshot the images that speak to me and collect them all, so that I can organize them in a keynote later. When in the keynote I start filtering through them and analyzing the images: what do I like about it and why. After that I start to think about how I can use certain elements in my work. I do not use everything directly once I filtered through it all, but I use it as a starting point to know more precise where I'll go.

So basically I just let a tsunami of information get to me and I throw it in a keynote so I can look at it from an auctorial view and analyse what I like about and go into a deeper layer.
When to

At a certain point in your project you'll start to funnel your ideas to a more specific thing. This is a great moment to go to Google and get that visual inspiration that you need.
How to

Search for the images that you need and do not be afraid to click further, away from your original search word. This way you'll gather a lot of information that you can use to funnel even more and eventually finalize.