I use USPS standard first class. I also offer priority and express priority through USPS. The mailing system is very accurate, but once in a few 100 mailings something might go wonky. Buy insurance if you have doubts.
PayPal preferred but also accept direct pay with card through Etsy, and money orders sent to me.
Returns & exchanges
Ok, here we go. I pack everything with care and send your items to you using the UPS. If you do not receive your package contact the post office. That is what I would be doing on my end of things. I recommend your item be insured: this is what it is for. In the past I have unconditionally sent refunds if an item is lost. I cannot keep this policy: if you are overseas, I can only track the package as far as the USA border. I truly WISH I could hand deliver these gems to all of you, but I am at the mercy of the shipping industry and try my very best to get it to you. So the blunt answer is as follows: if your item is lost, I will not issue a refund--use insurance.