20. Know your tone. If you're writing a comedic list, don't give it an analytical spin. If you're writing a very serious, in-depth analysis, then provide the information you need to provide. Understanding the type of list you're writing is very important; all lists have a place, but if you're trying to describe the Top 10 Funniest Video Game characters, you might want to go with a funny list rather than analyzing the humor of those characters.
21. Avoid assumptions. The majority of people reading your list probably haven't played every game on it, so don't assume they have. Give a little bit of backdrop on the particular item so that even if the person hasn't played the game, they have some idea why it's being included. Then, when describing why it fits your list, be specific. Don't just say, "We all know Solid Snake is one of the deepest characters in gaming": describe it a bit. Assume it's your mom reading your list, who probably knows nothing about video games. Sure, she might not be interested, but is your list at least informative enough for her to understand what you're describing?
22. Deal with spoilers intelligently. If your list topic doesn't need to spoil the games it lists, don't. You can allude to big plot events or character developments without spoiling them if they aren't the focal point of your list. Try lines like, "Cloud's character development truly accelerates later in the game, making him one of gaming's more interesting characters." That line doesn't actually spoil anything from the game, while still allowing you to justify including the item.
If your list is inherently ridden with spoilers -- for example, Top 10 Final Bosses -- then by all means, mark the list as a whole for spoilers. In those cases, I'd also recommend not putting any spoilers in the game's title line: that way, someone could scroll through the list and see, for example, Final Fantasy VI and think, "Oh, I'm playing that right now, I don't want to see what the final boss is" without preventing them from reading the rest of the list.
But sometimes your list might fall somewhere in between these extremes. For example, think of a list about Fathers and Sons, like Sanctuary Remix's. Certain father-son pairs in that list, like Tidus and Jecht, are known from the very beginning of the game. Others are enormous spoilers for their respective franchises. For these cases, I recommend doing what owned2dabone did in his list of Electricity users: state in your introduction that you'll mark sections that contain spoilers with an asterisk, and follow the previous paragraph's advice about not putting the spoiler information directly in the section title. That way, someone can scroll down, see the asterisk that indicates a spoiler, see the game title, and decide whether to read the section or move on.