I'm in the US and international rules are confusing to me. I've sent a number of cards to Germany, and I always just take the cards to the post office and they just put one of the international poinsettia stamps on there. When I sent a card to Serbia, they weighed it and it cost more (although this was at a different post office). I have some cards I am planning on sending to India and Thailand, and I guess I will just be taking them to the post office like I normally do, but is there an easier way that doesn't involve me going to the post office so much? I don't know how you know which countries are just ok to use the international stamps with or when things have to be weighed. I never send anything more than just a regular card in an envelope, so they're not heavier than normal mail or anything like that.

Thanks in advance for any advice/information! I want to make sure people in other countries still have opportunities to receive cheer :)