Buy and read Daniels running formula. It's best feature is the way work/rest ratios are easy to figure out. I was a clueless runner until I read it because work/rest ratios were often a mystery or imprecisely defined. Then Use Jack's online calculator to find training paces based on a recent race (not goal pace, an actual result)
http://www.runsmartproject.com/calculator/
Repetition: equal distance recovery with no time restrictions. 400s & 200s. Example: 400m repeats with 400m jog recoveries in between. hard running is 5% weekly mileage.
Interval: equal time recovery. work time should be in the 4-5 minute range. typically 800-1200m. Example: 1200m repeats with a 400m jog that is limited to the time it took to run 1200m. hard running is 7-8% weekly mileage.
Threshold: 1 min recovery for each mile you run. Example 4x1 mile with 60s recovery, 2x 2 miles with 120s recovery. hard running is 10% weekly mileage.
You also infer from his notes and guidelines that a full workout on the track (including recovery) is typically 8-10% of weekly mileage, often maxing out at 10k.