IN 2012, the Pope joined Twitter, President Obama sent the most retweeted post and the site announced that it had surpassed 200 million active monthly users. This was also the year when some tweeters came a cropper, either by saying something they shouldn't, tweeting information that was in contempt of court, or drunkenly spouting off. From the Lord McAlpine allegations that surfaced on Twitter, to the naming of the victim in a child abduction case and the conviction of a number of football supporters for issuing racist tweets, it has been a year of many lessons. A grand experiment is taking place. The mistakes of others are leading us to form a set of rules for the social media platform. Here, then, are those rules, as delivered on to us through what came to pass in the Twittersphere in the year of our Lord, 2012.

1Thou shalt treat each tweet as if it were a publication rather than a random drunken rambling in a bar. Indeed it's probably best to mug up on the law as it applies to journalists. Then, hopefully, you will not, as Sally Bercow did earlier this year, name a victim in a child abduction case. The Speaker's wife had to eat humble pie and ultimately ended up closing her Twitter account. Of course, Bercow, an inveterate tweeter, was back online soon enough, in November, when she got her account running again with the words: "Humbly reactivating account on£Levesoneve *grabs tinsel & mince pies* coz learnt lesson, miss Twitter & will not screw up again. Hello!"

2 Thou shalt not bear false witness. Even on Twitter, slandering or even hinting at possible lies about someone, is not wise. It's even less of a good idea when those false accusations involve child abuse, as they did with the misnaming of Lord McAlpine on Twitter, following the false allegations on Newsnight that a "prominent Thatcher-era Tory" was a paedophile. Among those who tweeted his name were Guardian journalist George Monbiot, serial tweet-bungler Sally Bercow, and the comedian Alan Davies. From this we learned it's not possible to hide behind vagueness or ironic emoticons, as Bercow did when she tweeted to her 56,000 followers: "Why is Lord McAlpine trending? *innocent face*". Or Monbiot did by writing: "I looked up Lord McAlpine on t'internet. It says the strangest things."

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3 Nor shalt thou retweet the slander of others. Alan Davies was among those whose error was to do no more than retweet a name. After first asking, "Any clues to who the Tory paedophile is?" he retweeted the response to his 444,000 followers.

4Thou shalt not commit misogyny. In May, then-Tory-MP Louise Mensch decided to call the women-hating trolls for what they were. Highlighting the abuse on Twitter, she told her 50,000 followers: "Women too often shamed into silence. Sod it." She then retweeted the worst examples, including one that described hitting her in the face with a hammer, saying: "I've added a few more favourite tweets to show the misogyny. I could do this all day." The sisterhood and much of the Twitterhood got behind her, and she received a deluge of support.

5Thou shalt not make racist remarks. Even when you are drunk, as Liam Stacey found out when he posted offensive comments about footballer Fabrice Muamba. The Bolton Wanderers player had collapsed on the pitch and Stacey's response was to tweet: "LOL, F*** Muamba. He's dead." Stacey was received a 56-day prison term for a racially aggravated public order offence. However, Stacey is not alone in this Twitter trend, which has been given the name twacism. Newcastle University law student Joshua Cryer, 21, admitted using the social networking site to bombard ex-footballer-turned-broadcaster Stan Collymore with abuse in an attempt to "snare a celebrity". Cryer was given a two-year community order for his actions.

6 If, however, thou art widely recognised as a funny man, then you can probably get away with jokes that are in bad taste. This, after all, is how you make your living. As comedian Frankie Boyle put it following the indignant reaction to his Paralympics comments: "I'd say my Paralympic tweets are celebratory. I'll be joking about Paralympics same way I joked about the Olympics. That's my job yo."

Contrast this with the fate of those who indulge in black humour, but are not professional comedians. Matthew Woods, for instance, whose insensitive quips about missing child April Jones got him three months in prison. Or Paul Chambers, who was finally acquitted of his 2010 conviction for tweeting the gag: "Robin Hood Airport is closed. You've got a week and a bit to get your s*** together otherwise I am blowing the airport sky high!!"

But also comfort yourself with the fact that times are changing. New guidelines issued last month by the director of public prosecutions in England suggest that even nobodies might be able to get away with a bad taste joke in 2013. Drunken Twitter-users who post grossly offensive messages online will be less likely to face prosecution if they delete the message and apologise after they sober up.

7Thou shalt not take the trolls too seriously. One example of fine-handling of vicious tweet behaviour was performed by young diver Tom Daley during the flurry that became known as the "social media Olympics" in August this year. A Twitter troll had sent a tweet telling the diver, whose father died of cancer last year, "you let your dad down" when he failed to clinch a medal. Daley's own response was a virtuoso slap-down. Rather than close his Twitter account, as many said he should, he retweeted the original post, saying: "After giving it my all- you get idiots sending me this."

8 Twevenge is a dish easily served online. Indeed, it's the fast food route for getting back at those who have betrayed you. Following the break-up of her marriage, for instance, Scottish entrepreneur Michelle Mone recovered from rumours about her ex by tweeting a picture of herself looking particularly glam, and saying: "Having a ball with kids. Started my 8 week intense training, lots of egg whites, veg and Chris Brown. Why don't you do it too?"

9 Know when the time has come to delete your account. Singer Chris Brown hit that point after he got involved in a vicious and vitriolic spat with the comedian Jenny Johnson, which descended into unrepeatable insults. But others celebrities have deleted their account this year, too. Singer Adele, for instance, quit the social networking site back in November, after Twitter trolls bombarded her with insults and taunts when the news broke that she had given birth. Remember, not every life has to be lived on Twitter.

10Thou shalt show the world you care. Justin Bieber's "RIP" tweet about Avalanna, the six-year-old fan whom he "married" and who died of a rare form of cancer, was the second most retweeted message of 2012. It was reposted 220,000 times and was only usurped by the massive Twitter surge that followed Barack Obama's 2012 presidential victory, and the 810,000 strong retweet of: "Four more years".