This is a tough question to answer. Drills are a good way to warm-up, some coaches think they reinforce good form, but the research is mixed. Your best bet is to practice faster running in a pair of lighter shoes that have a minimal heel-toe drop (the heel isn't elevated that much). It's much easier to land on your midfoot when you're running faster in a shoe with a lower profile. It takes awhile to change your form, and it's often difficult, but this is a good strategy.

Additionally, an important aspect of form to consider is not where on your foot you're landing, but where on the ground. Landing underneath your center of mass with a quick cadence of about 180 steps per minute is more important than landing on your midfoot. Having this high a cadence and landing directly underneath your body will also help you to land on your midfoot.

Good luck!

- Fitz.

PS. I wrote a longer post about improving your running form that you may enjoy - http://strengthrunning.com/2010/06/how-to-run-like-chris-solinsky-improve-your-form-to-prevent-injuries/

There's plenty of videos on youtube if you serach for pose running or chi running.