Well, first and foremost, regardless of your country, make sure you have a nice, stiff drink. You'regonnaneedit.
Ad Hominem attacks: Shout "Ad Hominem!" in unison and take a drink. Take a second drink for mispronouncing Ad Hominem.
If one person repeats the same point, drink! Really, for most debates, this rule alone will be plenty, and needs to be narrowed down with these rules:
1. Each point should involve a specific word that directly harkens back to that point. Then that word can be used as an unambiguous trigger to drink.
2. Each trigger should be one specific petty issue, not a broad idealogical stance. Since the petty issue can be brought up with just a few words (or even one), it's common practice for politicians to bring them up again and again in the middle of bigger, unrelated arguments. This is much harder to do with real issues, so don't use those (don't worry, they don't come up very often).
3. Try to focus on points made as early as possible in the speech\debate; these are most likely to be repeated a lot.
The 2011 Canadian English-language election debate is a sterling example, where in the first question of debate (point 3), the opposing leader criticizes the ruling party's budget for including "jets" and "prisons" (point 1), and repeats these two words many times throughout the debate without elaborating on them (point 2). In some debates, the petty talking points won't be so obvious at first, but if you keep listening, a few concrete ones will make themselves apparent.
Every time a major political official is caught in a sex scandal, drink three shots of tequila out of a hooker's navel.
If the politician in question was a noted male opponent of gay rights and the sex scandal was with another man, drink three shots of appletini instead.
Canadian election debates have a monitor who has the job of making sure every party leader has a chance to defend any points being made, and to ensure everyone gets roughly equal speaking time. One drink if someone speaks out of turn, and another drink for every time the monitor repeats the name of the person who is supposed to be talking, or otherwise protests.
Take a swig of Vodka and shout "Budem zdorovy" every time somebody attempts to shoot down a policy or idea by calling it fascism, socialism or something similar.
When a major politician changes his policies entirely upon election, drink a Black and Tan
When a major politician is simply accused of this by people who didn't pay any or enough attention to what he was promising, drink one of the two colored ales straight, smashing the other one over the head of the person in question
When a US presidential hopeful tailors large parts of his initial campaign towards Iowa, take a shot of corn whiskey
Take a shot every time somebody filibusters
For a fun variation, take a shot for every hour the filibuster goes on. IMPORTANT NOTE
this side-game only works when actual filibusters are required. At the moment, the mere promise of a filibuster is sufficient, meaning they can effectively last for months or years, and as such the variation is, for the moment, suicidally insane
Take a shot every time somebody uses the phrases "balanced budget", "national debt", "federal budget deficit", and "selling our country to the Chinese". If anybody actually accomplishes anything meaningful on this, down the entire bottle, and any other bottles you have in the cabinet.
There was one for the 2008 presidential debates. Take a drink any time Obama stammered or said "Let me be clear". Or drink every time McCain said "Maverick" or "My friends..."
Whenever a candidate for any office mentions repealing an amendment take a drink. Take two if said candidate has already show a lack of understanding of any of the amendments in the constitution.
Whenever any politician strongly opposes a nonexistent strawman, take a shot through a straw.
Whenever a Democrat accuses a Republican of "Wanting to take us back to The Fifties," down a shot of vodka. Whenever a Republican accuses a Democrat of "Wanting to take us back to The Sixties," down another shot.
Whenever one party votes against something that they ideologically would at least partially support just to spite the other party, take a shot. If they propose something nearly identical once they get into a dominant position, down the bottle.
Take a sip every time Julia Gillard dips her head as she speaks. There's a reason why my father and I have nicknamed her "Dippy Ostrich".
Whenever President Noynoy Aquino has a speech, especially long ones like the State of the Nation Address, gather your friends.
Prepare various alcoholic drinks and liquor, cups, and shotglasses.
If he mentions Gloria Macapagal Arroyo, everyone drinks a cup of beer.
If he mentions his love life, everyone drinks a shot of tequila.
If he mentions his mother Cory, everyone drinks a shot of gin.
If he mentions his father Ninoy, everyone drinks a shot of rum.
If he mentions BOTH OF HIS PARENTS in one sentence, everyone drinks two shots of gin and two shots of rum.
If after the end of the speech, he mentions all of the above, everyone drinks all the remaining liquor on the table (that is, if there's anything left).