How to play Uno well once you know the rules: the decisions that matter, and the habits that win.
The player who wins is usually the one who never has to draw. Try to hold at least one card in each colour for as long as you can, and when you have a choice of cards to play, play from the colour you hold most of, keeping the singles as escapes.
Changing colour with a number card is often better than playing a wild. A red seven on a blue seven switches to red just as well, and it keeps the wild for a moment when nothing else works.
A wild is your best defence when you run out of the current colour, and a wild draw four can stop a player who is about to go out. Holding them for the end of a hand makes sense.
But wilds score 50 points in the winner's hand and action cards score 20. If another player is down to one or two cards, play your high-scoring cards before they go out, rather than being caught holding them.
Skips and draw twos hurt the player next to you, so think about who that is and save them for when that player is close to going out. A reverse does something different: it hands the next turn to the player on your other side, which makes it the card for steering play away from someone who is about to win.
When you are low on cards yourself, draw twos and skips are strong finishers: they stop the next player from changing the colour away from you.
When a player draws instead of playing, they probably have no card that matches the pile. When you change colour, choosing that colour again puts them under pressure.
Pay attention to which colour a player names after a wild. They picked it because they hold it, so avoid leaving it on the pile when they are about to go out.
A wild draw four is only allowed when the player holds nothing in the current colour, and you may challenge it. If they did hold that colour, they draw four instead of you. If they did not, you draw six.
Challenge when the player had plenty of cards and had been following that colour recently, or when the colour was just changed to one they had been playing. When they have only a few cards, or had just drawn, the play is probably honest, and the extra two cards are a real price.
Two penalty cards for forgetting can undo a whole hand of good play. Make it a habit to say it the moment you play your second-to-last card, not after.
And catch others: when a player gets down to one card without saying it, call it before the next player takes their turn.