You are asking a valid question and receiving a lot of good info.
when i list a sale I make sure to disclose EVERY LAST DETAIL about the watch, along with photographs. I make the terms of my sale extremely clear in the sales post, I also go over those details via PM with the buyer and make sure he/she understands and agrees. If there is any doubt between the other party and myself I pass on the deal. I make sure to list in the sales post what kind of shipping I use, how it will be packaged, how I will declare the parcel. Again, i go over this info with the buyer prior to accepting payment. I tell the buyer I will ship however you instruct me, declare how you instruct me, and based upon that the shipping and customs risk is on the buyer. If the buyer is not happy with that, or we can't agree, simply walk away from the deal.
Despite the fact that I always agree with the buyer that I am not responsible for shipping or customs, assuming that I have followed exactly what we have agreed upon, I will do everything I can to resolve a problem that may arise. That means I will contact the courier and enquire about the parcel. If needed i will open an investigation. I will stay in contact with the buyer via pm or email all the way until they tell me the package has arrived safe and sound and that they are happy. If I can't post the parcel when I agreed to, I will let them know ASAP, apologize, and recommit. If I won't be able to answer their messages for any reason, I will let them know in advance so they won't worry.
If you read and understand the rules of RWI, take care in how you treat other members, be clear in your communication and have integrity in your word, I assure that you will be fine.
If you intentionally scam other members, or have the worst luck on the planet and act completely negligent in your responsibilities as a seller and forum member, then you end up here. 99% of the time if you are in the brig over a sale or a number of sales, the reason is explained by the former.