These points will hopefully help you get the most from your seller:
Remember the weekend! - First of all I think its worth mentioning as a seller that a buyer should never email on a Monday morning saying they ordered something three days ago and it still has not arrived.
Dont always use special! - When returning an item that costs less than around £70 you dont need to use special delivery. Around 99.7% of first class parcels get there the next day but the post office make their money by selling you extra services you dont need. Most buyers will not refund special delivery if thats not how it was sent. Just use the same service that it was sent to you by.
Dont ask if your item has been sent - If you email a seller asking if it has been sent you are only waisting your time and the sellers time and slowing the process down. If the seller has good feedback they probably send the same day or the next day. I know how tempting this can be, I have done it in the past too!
Dont make threats - If you have a problem dont tell the seller "will neg them" or "report them". We all know what happens when a buyer is not happy and sellers will usually go out their way to help. All you need to do is explain whats wrong and the seller will take steps to correct it, then you can take the corrective steps.
Check your spam folder - Some email providers block automated ebay messages or emails with script that show pictures and links. If you havent had a response, this might be why.
Hope that helps.