Tips: The  Editor

Backups
Don't underestimate the importance of creating frequent backups. ROM hacking always carries a risk of bugs and problems, especially when it comes to NES ROMs, where data is re-used or convoluted with tricky memory saving techniques. Its not unheard of for a person to put a large amount of effort into a level hack, only to find that at some point something happened to cause the game to stop working correctly. If you have frequent backups, however, you can look back through them, find the most recent version without the problem, and probably even identify exactly what was done that caused the problem. And if you test your game frequently you are more likely to catch a problem sooner.

For this reason, Editroid has a menu shortcut to create a backup for you: Special Tools à Create Backup. When you create a backup, it will be saved in the same folder as the ROM. The map data will always be saved inside the backup ROM (rather than in an external .MP file). You can choose the file extension under the options menu (you can select either .BAK or .NES). The file is automatically named with a timestamp in the format of YYYY_MM_DD_hhmmss (Year, Month, Day, hour [24 hours], minute, second) with the extension you have selected in the options. For example, a backup filename might be named 2006_12_25_162000.BAK or 2007_04_01_230116.NES. Because they are named this way, sorting backup files by name will also put them in chronological order.

Metedit
Metedit is another ROM editor for Metroid. Metedit has its own set of features and you may want to use both editors in conjunction. Editroid and Metedit each have their own map system, however and they are not compatible. In order to use both editors together you will have to maintain a map for both editors. You will also have to make sure that your Editroid map data is saved to an external file (under the options menu). Metedit will reject ROMs with extra data.