Easy HP Regain
Have one member of the party cast regen on the whole group and command another to cast a spell. Before they do this, open the lid on the playstation. The spell will be unable to load, but regen will still work. You HP will still steadily climb.

Opening the Safe in Nibelheim

Be very careful opening the safe.. You will have a time limit. The combination is: 36 Right, 10 Left, 59 Right, 97 Right. You will fight a boss and then find some interesting items.