The screenshot above shows the results of a Splatoon 2 match I played over the weekend. You'll notice my team won by a tenth of a per cent. If you look closely, you'll also notice how the other team could've stopped us.
In Splatoon 2's standard "Turf War" matches, you don't win by splatting a bunch of opposing players with your ink gun. You win if your team collectively covers enough of the level in ink. Taking down other players is helpful because it slows them down and frees you up to spray more of the level, but when it comes down to it, the ink is what decides things.
My team beat the other team by 0.1%, which is basically as tight a margin as is possible. If you look closely at the map, you can see one glaring issue with the losing team's strategy:
That's right, they failed to fully ink their spawn. If they'd simply turned around and covered the area behind and to the right of their spawn point, there's a good chance they would have gotten the coverage they needed to end the match in the lead.
Above: One of the first player-created messages I saw when I started the game on Friday.
I gather that "Ink your spawn!" is a well-known thing among Splatoon fans, both because it's practical advice and because so many players fail to remember it. Let this be a reminder as you head into The Reef or Inkblot Academy in pursuit of glory: don't forget to ink your spawn.