I'm coming off of a layoff from running. I've been running consistently for about 5 months now. Over the last few weeks I've added some gentle strides after some easy days. I think I'm ready to start doing some speed-maintenance type work. For me, what's worked in the past is a rotation of the following three basic workouts (each appx 15-20min total length, not including warm-up or cool-down):
1. Tempo run
2. Long hills
3. Fartlek
So, which one should come first? I'm thinking the fartlek because it's so much less structured. But, the tempo run would be at the slowest overall pace. I've always liked hill workouts, and I include the long hill on nearly every run.