When to schedule H-1B stamping in Canada?

I’m currently working in the US on OPT and I’ve got an approved H-1B petition for Oct 2013 start. I understand that I need to travel to a US consulate overseas for H-1B stamping. So I’m planning to go to Canada in September to get it done. My question is: When can I schedule my interview in September with the US Consulate? Can I submit my DS-160 application form online RIGHT NOW and schedule an interview in September? Or do I need to wait till July-August before I can setup my September interview?

Thank you! Look forward to your reply.

It is not mandatory to get H-1 visa stamped if your COS has been approved. Check your approved petition - if it has an I-94 attached to the bottom, then COS has been approved and you will automatically move to H-1 status from Oct 1.

There is no need to go for stamping in this unless you have other reasons to travel outside of US.