My $0.02:
1) Sanitation, sanitation, sanitation.
2) Make a starter. Pitch big (into cool, well oxygenated wort)
3) Even for extract, do a full boil. Try to get at least a 30 qt (7.5 gal) kettle for 5 gal. batches.
4) Ferment at a steady, appropriate temperature.
5) Did I mention sanitation?