Ask yourself:
1. Is the card valuable raw?
rookies
full arts
numbered cards
golds/silvers
vintage holo
2. Will a higher grade increase resale?
If yes → grade it.
3. Is it a long-term PC (personal collection) card?
Grading protects it forever.
4. Does the card look clean under a bright light?
If you see lots of scratches → probably not worth it.
5. Is it rare or low population?
Then a high-grade pop is extremely valuable.