Emmy, warm ups,
easy paced run, no warm up needed.
Quality session/ (track/tempo) or race, progressive 3 1/2mile warm up, starting at easy pace, going through steady, and ending with 5 or 6 strides.
Then you're ready to hit the top paces.
Clearly it's all relative though. If you're running 15-20miles a week, you're not going to be needing to do a 3.5mile warm up for anything!