1. Participants (those engaging in sexual activities, per person, per

One drink just for the person being in a lemon scene.
If the person is 12 years or younger: one drink.
If the person is 30 years or older: one drink.
(You will need to decide ahead of time whether this applies to actual or
apparent age, to handle such folks as Urd and Washuu).
If the person is an extraterrestrial: one drink.
If the person is an artificial being (cyborg, clone, etc.): two drinks.
If the person is a being from Japanese folklore: two drinks.
>From some other culture's folklore: three drinks.
If the person is related to another participant: chug.
If the person is normally an enemy of another participant, and the sex is
consensual: chug.
If the person is a tentacled monstrosity: one drink.
And it's not a rape scene: finish the bottle.
If the person is Ranma, and a gender change occurs, calculate drinks for
both male and female forms.
If the person is the author: open and drink an entire bottle, then yell at
them for writing a the worst kind of "self-insertion" ^_^ fic.
If the person is being coerced: chug.
If the person is married: one drink.
To one of the other participants: chug.
And no one else is engaging in sex: finish the bottle and commend the
author for promoting "family values."

2. Setting (where the lemon scene takes place, per scene)

In a mecha: one drink.
While the mecha is operating: another drink.
While the mecha is engaged in combat: chug.
In outer space: one drink.
While weightless: another drink.
In another dimension: two drinks.
One another planet: two drinks.
In the past/future (time travel involved): three drinks.
In a dojo, shrine, or temple: two drinks.
During a magical ritual: two drinks.
In public: two drinks.

3. Activities (what happens during the lemon scene, per scene)

If a character's powers or equipment are used for sex-related purposes:
one drink per power per use.
And the character yells the name of the power/device in question while
using it: two more drinks, per occurence.
If a character creates a device for use in the lemon scene: chug.
If "protection" is discussed: one drink.
Actually used: chug.
For each orgasm: one drink.
If a female character fakes one: chug.
Someone gets injured during the sex act: one drink per injury.
And they keep at it: chug.

4. Writing

Every time the words "throbbing" or "engorged" are used: one drink.
If a author uses a sexual metaphor based on a character's powers or
possessions ("Mousse revealed his massive hidden weapon"): two drinks.
For each body part synonym: one drink when the word is first used.
If the length of a male character's member is mentioned: one drink per
inch beyond five, each time the measurement is mentioned.
If the measurement is given using the metric system: one drink per
centimeter past twelve, and check out the big brain on Brad!