I lightly drag the blade across my thumb - maybe at a 45 degree angle - and if it catches pretty good on the friction ridges then I feel it sharp enough for what I need.

I sharpen my knives using a Spyderco Sharpmaker which does a great job pretty easily. If you're using a Sharpmaker on one of Doug's Mkx knives, don't forget to use the 30 degree holes to maintain the original angle.