LGA-DFW-HKG is an easy way to get the bulk of the miles. For example, out 10/18 return 10/20, $959, 18980 miles. Available most days till early December, a little cheaper on weekdays. If you decide on that, then add in your domestic trip miles (or best estimate), and see exactly how many more miles you need. Then you can plan that trip to finish it off.

Take a look at the mileage run deals forum. There are some things in there that are pretty good, like the cheap PHL-LAS trip on US, or that BOS-MEL-YYZ on BA. A great deal could make a starting point outside of NYC worthwhile.

Don't waste too much time thinking about snaking around on your domestic trip. Although every mile helps, you need big miles and snaking around isn't going to make that much of a difference.

As previously stated, get this planned now and tickets bought. You want to have this done by the first week of December or you will pay a lot more.