Since you want specifically Delta miles, not just any miles, check the posts in the Delta forum. There are many threads there with ideas. If you can't find what you need there and have a specific question, posting it there will catch the eye of the Delta experts sooner than they'll see it in this general forum.

If I recall, the Netflix miles post rather quickly (couple of days?). That was though Continental but I imagine it's the same with Delta. The 1st month cc charge will show up on Netflix "accounts" page but they don't really knick your credit card for the first month.

1-800-flowers miles post fairly quickly - need to send easter flowers to anyone?