Create a save outside the core so you can go back and finish the "Lighthouse" side quest for the best gear. Safeguarding Against Corruption

A common "burnout" point. Keep a save before the boss to ensure you don't get stuck.

Older saves found on sites like GameFAQs often use the .gme format. 2. PlayStation 3 / PSP / PS Vita (.VMP, .PSV)

Once you enter the final sequence of Disc 1, you are on a "railroad." Keep a save before entering the forest leading to Solaris.

Xenogears is notorious for freezing at the end of Disc 1 or during specific cutscenes on hardware or older emulators. Having a save right at the start of Disc 2 can save a playthrough.