Vortica keeps it short and sweet. Just the tip. We promise!
Any time you have the slightest doubt on the DGC, you should immediately stop, and ask yourself what is causing that doubt. This may mean clamping down hard on your grip and not throwing the disc, and bailing out of your throwing motion.
Do not progress until you have established what is causing your doubts.
Your subconscious can sometimes see things or feel things you may not be completely aware of on a conscious level. Your grip may not be quite right for the shot, or your footing might not be perfect, or there may be an un-noticed dangler in your line of play.
Take a moment or two to assure yourself you have correctly assessed the situation before making your play.