This page answers some of the more frequently asked questions.
A: This depends on what exactly you want to modify. In some cases, there will be an editor to help you accomplish your task. I recommend browsing the utility page to get an idea of what is available. Some of the simpler and more noteworthy tools to start with include:
Tools for SNES version:
A: Again, it depends on what you want to do. Most people tend to start with one of two goals in mind. Either they have a specific hack in their mind that they want to create, or a specific aspect of hacking (spriting, events, enemy scripts, etc.) that they want to learn. It's probably easier to get started with the latter, as it's easier to focus on learning one thing at a time. If you're looking to focus on a specific area, you'll probably want to visit the Tutorials section of the Final Fantasy 3 (SNES) page, where you can hopefully find a link to what you are looking for. There are many hackers who contribute sprites, patches, bosses, etc. without creating a full hack of their own.
If you are looking to create a full-sized hack, note that you'll probably need to learn many different skills from different areas to succeed. It's unlikely that everything will be in your wheelhouse right away. In particular, note that many ideas may require heavy assembly (ASM) work to pull off and may be unfeasible. Don't be afraid to ask for help, but take note that nobody will make your mod for you. Also note that others will be more comfortable contributing if you can show that you have made significant progress on your hack. If you have made a lot of progress, it will become clear to others that you are less likely to drop the hack altogether.
A: If the game is violently crashing when you load the game, reach the first battle, etc., you are almost certainly applying the patch to the wrong ROM. There are two different versions of the game (1.0 and 1.1) that have minor differences. In addition, for each version of the game there are both headered and unheadered ROMs (see below). You have to apply the patch to the same type of ROM that the creator used to make the patch. Usually the ROM you should use is specified in the ReadMe or wherever you downloaded the patch from. Don't ignore this info!
A: A header is essentially just 0x200 bytes of padding (with some information that doesn't really matter to you) at the beginning of the ROM. There's not really a functional difference between a headered and an unheadered ROM, but you have to take into account the extra bytes when you are hacking. In many cases you'll want to simply remove the header using SNESTool, as it will make your life easier.
A: Zone Doctor is somewhat unstable and has a great deal of quirks. It may be usable if you learn how to work around them, but there isn't currently a solid source of info on what its limitations are. If you want to learn event editing, you will likely want to edit the hex code directly (it's not as scary as it sounds). Please visit the Event Hacking Tutorial page for more info.