Start with apparent condition
Condition is the first filter. A high-demand card with obvious whitening, creases, dents, or major centering issues may still be worth collecting, but it may not support the grading outcome you hope for. Check the front and back before you spend on a submission.
Consider the card itself
Look at the set, player or character, scarcity, and collector demand. Compare like-for-like cards where possible: the same version, language, condition, and grade can have very different appeal from a similar-looking card.
Include every cost
Add grading, shipping, insurance, supplies, and the time your card will be away. The decision can still be worthwhile for protection, presentation, or a personal collection even when resale value is not the goal.
Choose the outcome you want
Ask one question: if the final grade is lower than hoped, would you still be happy you submitted? If the answer is no, gather more condition information first and avoid treating any estimate as certain.