Most sunscreen advice is noise. In Queensland, four things do most of the work, and one mistake undoes all of them.

The standard advice in Australia is a sunscreen labelled SPF 50+ and broad spectrum. SPF describes protection against UVB, the burning rays. Broad spectrum means it also covers UVA, which drives ageing and contributes to skin cancer without ever giving you the sunburn warning. Both matter. A high SPF that is not broad spectrum is only doing half the job.
The single most common sunscreen mistake is not the brand or the SPF. It is using a fraction of the amount the label assumes. Proper coverage for an adult in swimwear takes about seven teaspoons: roughly one for each limb, one for the front of the torso, one for the back, and one for the face, neck and ears. Most people apply well under half that, which quietly slashes the real protection to a fraction of the number on the bottle. If your sunscreen never seems to run out, that is the clue.
Sunscreen wears off with sweat, water, towels and time. Reapply every two hours when you are outdoors, and straight after swimming or heavy sweating, whatever the label says about being water resistant. One morning application before a day at the cricket is not a plan, it is a hope.
Sunscreen is the last line, not the whole defence. The full set is the one you learned as a kid: clothing, sunscreen, a hat that shades your ears and neck, shade, and sunglasses. In Brisbane that applies close to year round, not just in summer, because our UV barely drops in winter. We covered that in this article.
Treating sunscreen as a substitute for ever getting your skin checked. Sunscreen lowers the dose going forward. It does nothing about the decades of exposure already banked in your skin, and it does not examine anything. Most skin cancers are very treatable when found early, and finding them early is a skin check's job, not a sunscreen's.
This article is general information, not medical advice. If you are worried about a spot on your skin, book an appointment with a doctor.
Full body skin checks in Bulimba, 15 to 30 minutes, no referral needed.