if really early, the guard post at the other end of the train tunnel on the second mission, if on the world map, try mideel area or wutai are, if in the last part of the game, the northern cave,
- The general area around Mideel is great for getting large quantities of AP fast at the end of the game if you don't wish to enter the Northern Crater (especially in the forests, if using the Slash-All materia and a double-AP weapon)
- Once you can enter the Northern Crater, anywhere up to the room where the party splits up, you can leave the Crater as many times as you like; this place also allows access to certain Enemy Skills you may have missed or can't otherwise get (Laser and Dragon Force can be gotten by Manipulating a Dark Dragon.) The Northern Crater will get you boatloads of EXP, AP and Gil, but it's more dangerous than the Mideel area, and if you go too far (or use the Save Crystal in the wrong place) you might not be able to leave the Northern Crater and return to the World Map.
- The part of Junon Harbor leading to the Underwater Mako Reactor is great for getting people's Limit Breaks, since the Death Machine does decent damage reliably with 100 Needles and W Machine Gun, and is easily manipulated to ensure it injures the right person (since use of Limit Breaks is often how to get more Limit Breaks)
- Goblin Island is the only place you can get the Enemy Skill "Goblin Punch" (which is also only useful if you're trying for 100% game completion)
- It is possible to return to the area after the mandatory snowboarding minigame and before Gaea's Cliff. The enemies found there are good for EXP and AP compared to time, especially at the end of the game (before the final battle, after which the game simply ends completely)
- The forests around the Temple of the Ancients are an excellent place to encounter groups of four or five (very weak, low AP/EXP/Gil) enemies to one-shot-kill with Vincent (using the Slash-All materia) when trying to increase the power of the Death Penalty.