My 9-month-old golden jumps on every person who comes through the door. I tell her 'no' and try to push her down but she thinks it's a game. How do I stop this?

Pushing her down is play. Saying 'no' means nothing to her. You're giving her exactly what she wants: contact and attention. The behavior works. Here's what actually stops it: jumping gets her removed from the situation instantly. When a guest arrives, have her on a leash. The moment her front paws leave the ground, turn and walk her into another room without a word. Wait 10 seconds. Return. If she jumps again, remove her again. Repeat until she keeps four paws down for 3 seconds, then release the leash and let her greet. Most goldens need 8-12 reps before they stop offering the jump. You can't do this if she's off-leash when the door opens. The leash gives you the ability to enforce the consequence immediately. Guests will want to help by giving her attention when she's calm. Let them. That's the reward. If you've been pushing her down for months, expect an extinction burst — she'll jump harder the first few times because the old strategy stopped working. Push through it.