Now some things to consider -

1) How long did it take them to buy the products. If its more than 4 or 5 minutes how can you streamline the process.
2) Did they ever appear to get lost in the process - if they did get lost - where did they get lost at. Did you provide an easy map to get unlost?
3) Did they hesitate any during the order process - why did they hesitate. If something was unclear, what was it, how you can you make it clear.
4) Was it easy for them to find the second product. If not why? What can you do to correct it.

The order process should be no more than two or three clicks at the most to order.
At each stage of the order process - the next step should be outlined clearly - as well as instructions for how to do the current step.
Contact information - including a telephone number - should be provided in case folks get lost along the way.
Security of your site / pages / should be highlighted during the process.
Explain to people what you're going to be doing with their personal information.
Reiterate why they should trust you.
Perhaps include a testimonial or two within the process.

Tomorrow we'll talk a little about some questions you can ask your test subjects.

Tim