The bits you don't think about until you need them.

Leashes

A legrope is essential on most boards. Match its length and thickness to the board and the conditions you're surfing. It needs to be long enough to let the board move without creating unnecessary drag or getting in the way. They're usually labeled as being for a shortboard or longboard anyway so it's not hard to get right. Just don't use a short legrope on a longboard because the board can spring back too quickly and cause an injury.

Board bags

A board bag is useful even if you don't travel by plane. It protects the board from knocks in the car, on roof racks and while you're carrying it around. For everyday use, you don't necessarily need the most heavily padded travel bag. A simple board sock can often do the job.

Key safes

If your car key can't go in the water with you, a secure key safe can save you from hiding it under a wheel or hoping nobody notices it sitting on a tyre. Just make sure the safe is actually designed for outdoor use and is attached somewhere sensible.

Wax and traction

You need some way of keeping your feet attached to the board. Wax is essential and a wax comb is pretty useful too. Many shortboards come with a traction pad that helps you get your back foot in the right place. If yours doesn't you can buy one and add it easily yourself.

Changing mats and beach gear

A changing mat isn't essential, but once you've ended up with a wetsuit covered in sand in your car after changing on the beach, it starts to make a lot more sense. The same goes for a decent towel, changing robe or somewhere to put your wet gear.

Roof-rack straps

If you're carrying boards on a car, use proper surfboard straps and make sure the board is secured correctly. It's not the sort of thing worth improvising.

Ding repair

A small repair kit can be handy for minor damage, particularly if you're away from a surf shop. It isn't a substitute for getting a serious ding properly repaired, but it can stop a small problem becoming a waterlogged board.

Make sure you know if your board is epoxy or polyurethane construction because you'll need the right resin or quick fix to match.