I’m currently doing some shifts as a Christmas casual for Royal Mail (not a career change; just broadening my life experience while earning extra cash). Seeing how people prepare their post, and how it’s handled, has been eye-opening. Here’s my advice:

1. Put an address on the envelope. Then check that you’ve put an address on all of the envelopes before posting. Yes, we all think we do but my recent experience has shown a startling number of envelopes, some even stamped, with a first name only.
2. Sending something abroad? Add the name of the country! Wellington in New Zealand is not the only place with that name. Standing at the frame (postcoded pigeonholes) isn’t the best-equipped place for a sorter to work out where in the world you mean.
3. Lots of place names occur more than once within the UK, even within the same county, eg St Ives, Newport, Gillingham, Richmond… so it never hurts to add the county.
4. If your handwriting is tiny, consider writing slightly larger than normal. Not everyone sorting the post has perfect eyesight. And squinting gives you wrinkles.
5. Make sure the colour of the ink stands out against the colour of the envelope. If you find it hard to read, so will the sorter (who has to look at thousands of envelopes a day).
6. Breaking news alert: there are these things called postcodes. The last one for the UK was introduced back in 1974. Not sure of it? Don’t invent your own or leave it off. Look here: www.royalmail.com/find-a-postcode. Top tip: if you don’t know all of it, the first two letters are a big help. (Post is initially sorted into the areas designated by the first two letters of the postcode.)
7. If your handwriting is appalling scrawl, don’t be afraid to write like a child, particularly the important bit – the address.
8. Don’t write ‘local’ on the envelope. The person who opens the pillarbox doesn’t run round the corner to pop it through the letterbox; it all goes to a central office and is sent back out again.
9. Writing ‘fragile’ on a parcel doesn’t automatically consign it to a cushioned-as-a-cloud, feather-lined container. It may be gently placed in the wheeled crate in which it will leave the sorting office with all the other post. But another, heavier parcel may land on it later. See no.10. And see Royal Mail’s tips on packaging fragile items.
10. Wrap those parcels up really securely. They may be lobbed from a distance of up to four metres into the crates they’re transported in.