An example of some points I found helpful were to use high contrasting colours for different player pieces but to carefully think through the colours you want to use to make sure people who are colourblind can still distinguish the player pieces. Along with using different colours, you can use different shapes to differentiate the pieces too. A game can run a lot more smoothly and be a lot more enjoyable if different functions had different design components.
The article says that first impressions of a game come from its box which is very true meaning a lot of thought has to be put into the box design too and not just the game itself. Make sure to have the games name on the side of the box and think through how you want to print your game info so that consumers have choice in how they store the game.
After reading this, writing the rules of a game sounds a lot more difficult than expected. Some things the articles says you can do to avoid or minimise difficulties is to avoid writing very vague rules so that players can "decide for themselves how to play", it might come off as if the game isn't fully finished and another point was to give examples of where those rules apply to guide players and give a better understanding.
This article was very helpful and gave some good advice on how to design your game so that its a lot more enjoyable for players.