I need a quest chain for my soon-to-come modificaton, does anyone have a clue how to make one?

What do you mean by "chain"? If you just want the end of one quest to start another you use StartQuest in a result script somewhere, so I assume you have something more complex in mind.

Actually, I meant when you have finished one quest, you can go talk to the same person for another quest, like in the Dark Brotherhood.

It's usually handled as part of that NPC's scripting or dialogues. For instance, the condition for a dialogue can check for both a completed stage http://cs.elderscrolls.com/constwiki/index.php/GetStageDone and if a quest has been started http://cs.elderscrolls.com/constwiki/index.php/GetQuestRunning (make sure you uncheck "startgame enabled" ) which can then be used to start the next quest in the chain without having to be immediately started by the previous quest.

Thanks!