How do you write a prescription for a placebo of a drug like "atavan"?
What does the script look like? And, is there any indication or
writing on the label on the bottle that tells the pharmacist it's a
placebo?

The legislation regarding placebo prescription will very between
different countries.  Placebo will only be prescribed to people who
knowingly participate in an experiment.  In most countries, it would
be illegal for a pharmacist to sell a medication bottle containing
anything else than what it is supposed to contain.

It would not occur that a prescription would be written for a
particular drug, but placebo would be given instead. If the label
indicated a drug by name or chemical content, then if it isn't what it
says, a crime has been committed. If you mean "generic" instead of
"placebo," which means the same chemical but not the name-brand, that
happens all the time and is ok; the doctor indicates in some way that
generic is ok, either by writing it or checking a box. If one really
wants to give a placebo (a sugar pill that has no chemical effect)
then in general the patient must be aware that he/she may be getting
it as part of some sort of study. It used to be that one might write a
prescription for "obecalp" which is placebo spelled backward, and a
pharmacist might go along.

If you are given a placebo is it usually in the form of a sugar pill?
Does it vary? And does it taste like sugar?

>> If you are given a placebo is it usually in the form of a sugar pill?
>> Does it vary? And does it taste like sugar?

Sometimes lactose (also known as "milk sugar") is used as a placebo.
Lactose does have a somewhat sweet taste, but in compressed tablet or
capsule form the taste is not noticeable.