Suggestions for helping my client track sales conversions

It would also be nice if it could track conversions from a certain coupon code, so I could track print advertising, too.

Check out Google URL builder.

You can then use Google analytics for event tracking

If you use WordPress, then use this Plugin "Google Analytics"

Tracking of any type is all about the point of entry. Online advertising is obviously easy you can have an ad a place A goto page A of your site. Location B goes to page B etc. By developing the point of entry you can then use Google Analytics ( GA ) to track the specific traffic to each page and determine a rate of conversion.

Offline advertising is a bit different in a way, but very much the same. I use URL's like webaddress/offer15 - with a few different woocom plugins you can set up the coupon value based on the entry page, so the coupon is automatically added. And again the same applies, using GA to track from point of entry.

As much as we are wanting to track the final end conversion ( the sale ) you really want to focus on and track each of the smaller conversions along the way. How many make it to the landing page ( point of entry ) how many follow the next step and the next and the next.. are there disruptions in the flow that are causing reduced conversions?

So to say you get X amount of traffic, and made Y amount of sales looks good, but it really is only 10% of the story. the 90 percent n the middle is those smaller conversions and how the effect the end result. Focusing on the 90 ultimately increases the end result - the sale.

Google Analytics with URL tracking parameters. When using Adwords they are automatically added, but with other sources like Bing you will need to append them to the end of your URLs. If you also get sales from phone calls, you will want to add phone tracking to Google Analytics as well.