I think this should be said somewhere, because it saves typing for everyone else out there who has bugs to fix in their games.
Speaking from the view of someone who writes a lot of code (disclaimer: At the time of this writing, I am a 17-year old programmer by hobby alone), bugfixing is a pain in the ass. Even if you know where exactly the code is breaking and why (an occurrence that is way rarer for me than it should be), it's generally a struggle to make sure that everything works afterwards.
So you, as the bug reporter, can do a few things to make things easier. Most of these things aren't strictly necessary, but they're important enough of the time that it's probably worth mentioning.
The first thing that we (the creators) need to know is what happened. This seems self-explanatory, no? It's not enough to just say "the game froze during ravens tale wtf?????", you need to be more specific than that. In a perfect world, "the game made a weird screeching noise and turned red when I moved lucius during raven's tale" would be enough to find and fix bugs, but it's not. Unless the game creator is messing with forces they really shouldn't be (or are just extremely bad at this), it's more likely that you encountered some scenario that they didn't expect. For FE hacks in particular, things like enemy placement, turn events, area events, etc can actually interact in completely different ways if the developer didn't think of every eventuality (which, to be entirely honest, literally nobody does).
The easiest thing to do would be to include a save. That guarantees that the dev can recreate the bug, which gives them the easiest time of finding out what's going wrong. Barring that, it's important to include as much information as possible. If a fight froze, say who was attacking, with what weapons, at what range! If an event clutches up, provide a screenshot or something, or give as much of an idea of the general situation as you can! If an event is just plain /wrong/ (something like "here's a hero crest!" >vulnerary), it's still important to try and convey as much of the situation as you can. In some cases, it's a simple fix. In others, even the seemingly simplest of bugs can be caused by something seemingly unrelated! So throw the devs a bone.
Bad example: "the game froze during ravens tale wtf?????"
Good example: "The game stalled in the middle of Raven's tale after priscilla said something"
Best example: "The game stalled in the middle of Raven's tale after priscilla talked about going to her brother's side; after closing the dialogue window the game got stuck on the map and never did anything else. [screen]"