customer order form for shopify

*does anybody have any tips on setting up a custom order form for clients on Shopify? I need information from customers before I can start the order. What I do now is send them an email requesting the information but sometimes it takes the customer a long time to reply. So to expedite the process it would be easier to have them provide the info whenever they are in checkout. Is there a way I can do this on Shopify?

Send them a custom form where they will fill in the details for you and get redirected to the shopify page? Or something similar?

Add me in skype. Lets just discuss. My id is repulsorbhw

No. I need it to be on the shopify page. For example they are browsing the site, then they add what they want to the cart but before they can submit the order and pay, they have to fill out order information. Something like that.
And I will add you on Skype tonight. I'm on the phone right now.