For Terezi I have a bookmark folder full of homestuck references/resources, though it isn't just for her because I play a few other MSPA characters too. HOWEVER i do have a lot of panels that are relevant to Terezi bookmarked there, and also things like compilations of troll biology words used in the comic, text color resources, attempts at making timelines of the pesterlogs, links to outfits that Kanaya has made her/gifts that other people have given her...and also I have a text document on my computer with every pesterlog that Terezi is part of copypasted into it, so I can do a quick ctrl+F without loading the entire homestuck search page if I want to do a quick review of something she's said/done.

For Stein I have a text document with some pertinent quotes from the anime concerning his personality/philosophies/hobbies/etc. There are also some pages lurking in my general bookmarks about things like vivisection and medicine and things like that...

And for Czeslaw I just have the light novel translations bookmarked, heh. I reread them every once and a while so I don't forget things. When I played him from the 1930s I also had a few pages bookmarked concerning that time period, like a collection of slang terms from the 30s and the wikipedia page on movies released in the 1920s. And I also keep a text document with a few relevant quotes from both the anime and the light novels on hand for him.

One of these days I will make actual transcripts for Stein and Czeslaw....one of these days.