Where do you start?
With a promise to yourself, your boss, your company or client -- if the company can't measure the output don't spend the money.
So when finance asks for a breakdown of what the marketing budget was spent on, you can match that with a breakdown of the sales impact and what that means for next years marketing budget and sales figures.
These are just some examples:
X amount spent on a TV commercial promoting a sale item = X amount of sales of the promoted item.
X amount spent on billboard campaign with SMS short code = X amount of SMS reponses
X amount spent on branding campaigns in a year = X amount of uplift in brand recognition in independent surveys.
X amount spent on a print campaigns = X amount of sales with different discount codes.
X amount spent on an email affiliate promotion = X amount of leads generated.
X amount of spent on a trade show = X amount of sales meetings arranged after the event.
You get the picture.
Hmmm well I hear you say it isn't that simple in reality, as distributors won't give you the data, or there are issues internally that prevent you from using direct response techniques as that is owned by another department, sales won't tell you the effect of your campaigns, we don't have a CRM system to track that, or you have no analytical skills.
These are all excuses and yes it becomes difficult to measure across multiple channel campaigns, but it is still possible.
Keep that promise - if the company can't measure the output don't spend the money.