For the record collector, eBay is a great resource for buying rare and hard to find LPs, and for getting a good deal on new releases. Unfortunately, a lot of sellers (even those with predominantly good feedback) either don't know or don't care how to package an LP to make sure it doesn't get damaged in the post. If there's one thing I hate, it's thinking I've got a great deal on a new or mint LP, only for it to turn up with the edges frayed or the corners bashed in.
So, sellers: don't just stick the record in a cheap, lightweight LP mailer, label it as "FRAGILE" and hope for the best. All "FRAGILE" means to the goons at the local sorting office is that they should throw the package underarm! Spend a little time on packaging your records and it will pay off in happy, repeat customers.
1. Get some decent packaging materials
At the very least you will need: a good quality LP mailer (the thin, white card ones are not really adequate, use a mailer made from thick cardboard - a box is even better), 2 pieces of thick cardboard measuring just over 12"x12", bubble wrap, and some good, strong parcel tape. You don't need to buy new packaging materials. If you've received an LP in the mail, chances are you can save yourself some money (and help to save the environment) by recycling old packaging material - just make sure the bits you're going to use are in good shape (no splits, tears, etc.).
2. Remove the record from the outer sleeve
Records can shift about during transit, so if you leave the record inside the outer sleeve, you're inviting seam splits and ringwear - bad news! The good news is that you can solve this problem by removing the record and inner sleeve from the outer sleeve.
If your LP is still sealed, ask the buyer if they would like you to slit the shrinkwrap and remove the record - some collectors will tell you not to, since collectible LPs are usually more valuable if they're still sealed, but chances are, as long as you make your slit neatly and carefully (use a sharp knife or razorblade), anyone who is actually planning on playing the record won't mind. On the contrary, they'll likely be impressed that you care enough to ask.
3. Bubble wrap
Place the record (still in the inner sleeve) on top of the outer sleeve and wrap them tightly (although not so tightly as to bend the edges in) with bubble wrap. Secure with parcel tape.
4. Make a record sandwich!
Place one piece of cardboard on the table. Place the bubble wrapped record pack on top of it, and finish the stack with the other piece of cardboard. Use the parcel tape to bind the sandwich together tightly, so the pieces can't move about.
5. Place into the mailer
Self-explanatory, really. Make sure the records can't shift about too much in transit, and use lots of tape to make sure the mailer is securely sealed. Mark the package as "FRAGILE - Handle With Care" / "Do Not Bend" in big letters.
Now, it's off the Post Office to get this record off to a happy customer.