I have always help design my own pay plan and my team's pay plans. Depending on the dealer and set up, I have always tried to have a once-touched, then counted philosophy. It puts a lot of focus on tracking and inputting data routinely and then following up.
Once touched means that as soon as they e-mail in, call in, or fill out a coupon, that we, as a department, created enough call to action by either our ads or our responses to get them in.
Walk ins, unless centrally controlled, are not an exact science. Some stores and salespeople will report them, most will not. But I tell the dealers that a large portion of customers don't print maps, don't e-mail in and simply show up to the dealership. They don't inform the SR that they started the process online, and the SR doesn't ask.
Therefore, rather than beat my brains in trying to measure these people, I choose to focus on those we can count. I tell the dealer principle that by us "touching" the client that we gain valuable information that allows us to market to them in the future.
So, truthfully, the people might have bought anyways, might have been a repeat or a referral. The point is however; that these people did go online, and probably NOT to just our site or vehicles as statistics have shown. But they ended up buying from us, AFTER viewing our site our contacting the Internet department.
We had to do something right to earn their business.