I've never really understood whether it's better to make a new thread for a topic that's been previously discussed or to post on an older thread that was abandoned weeks/months ago. Personally I prefer to create new threads but what do you think?
Most of the time I pick new threads because often the OP of the old thread isn't around or is irrelevant or the information is outdated. If it's like...an old tutorial that you're asking specifically about I say necro.
Depends. If the thread in question is just a skeleton, conjuration is the way to go, but if there's still flesh on it then necromancy.
Find existing thread. 1. Is it your thread? If so, necro it. 2. Is it someone elses? Is it believable, well-constructed and still relevant? Necro it. If it isn't, create a new thread and link it in your OP for reference. 3. Don't necro unless you have something useful to say. Same applies to creating new threads, I guess tl;dr: both.
Necro. No matter how old a thread is, someone, sowhere will scold you for not using the search function if you don't.
If the old thread is no longer relevant. simply preface your OP for the new thread with a link to the outdated thread then proceed as normal. I have only seen one person scold users for creating a thread on a subject that may have been touched on before.
I would say one of the main problems with using reddit is that for something to be relevant you have to make a new thread, which the traditional forum format should hopefully solve. Which is why I say necromancy.