Wardriving in practice

The hardware is the easy part. What separates a useful drive from a wasted evening is mostly speed, antenna placement, and having a GPS lock before you start.

Antennas

An omnidirectional antenna is what you want for driving — it hears in every direction, which is right when you do not know where the networks are. Directional antennas are for finding one specific thing.

A modest external antenna beats a big one badly placed. Get it outside the metal box you are sitting in.
Magnetic roof mount is the classic answer. A window mount is second best.
More gain is not automatically better: high-gain omnis flatten their pattern, which means they hear further sideways and worse upward. For street-level driving that is usually what you want, but do not expect miracles.
Both 2.4 GHz and 5 GHz matter now. A dual-band antenna, or two radios, will find substantially more than a 2.4-only setup.

Speed

Access points beacon roughly every 100 ms, but your radio is hopping channels and can only listen to one at a time. At 50 km/h you cover 14 metres a second; at 110 km/h you cover 30. The faster you go, the more channels you never happened to be listening to at the right moment.

Walking: Best possible coverage. Good for dense areas.
30–50 km/h: The sweet spot. Residential streets are ideal.
80+ km/h: You will catch the strong ones and miss most of the rest.

GPS

This is the single most common way a drive is wasted. Rules that save evenings:

Get the lock before you move. A cold start outdoors can take several minutes. Moving during it makes it slower.
Watch it during the drive. If your setup can display fix status, display it. A receiver that drops out silently produces a file full of one repeated position.
0,0 is not a location. It is the null value your device reports when it has nothing. This site rejects those records, which is why an upload can come back as "no usable GPS fixes" even though the file is full of networks.
Tunnels, multi-storey car parks and dense city centres will lose you the fix. Expect gaps.

Routes

Coverage beats distance. A grid of residential streets driven once will yield far more than the same time spent on a ring road.

Drive streets you have not driven. Re-driving adds sightings to known networks, which is useful for accuracy but adds nothing new to the map.
Repeat passes do improve position accuracy — this site keeps the strongest-signal fix as canonical, so a second closer pass corrects the first.
Check the map before going out. Empty areas are worth more than filling in gaps.

Law and etiquette

In Denmark and across the EU, passively receiving broadcast beacon frames is not the problem — those frames are transmitted openly to anyone in range, which is how your phone finds networks. The lines that matter:

Do not connect. Not to open networks, not "just to check". That is unauthorised access, and it is a criminal matter.
Do not capture traffic. Beacons and probe responses only. Payload capture is interception.
Do not attack anything. No deauthentication, no handshake capture, no cracking. If you want to practise those things, do it on your own gear.
Respect requests. If someone asks for their network to be hidden from the map, hide it. It costs nothing, and the alternative is the community developing a reputation it does not want.
Think about what a map means. An access point is often a home. Under GDPR, location data tied to identifiable premises deserves care even when it was broadcast in the clear.

Nothing here is legal advice. If you are unsure about something, ask in the Discord before doing it rather than after.

Getting the most out of the archive

Upload the raw file, not a filtered subset. The parsers throw away what they cannot use, and keeping everything else means the data stays re-analysable.
One file per drive is easier to review than one file per month.
If a dump gets rejected, read the reason — it is specific, and it usually points at a fixable hardware problem.
Hide your own street if you want to. Nobody will ask why.