For minions, you want two things - something memorable, and something fairly easy to adjudicate. I like to pick one cool item/feat/power for my flunkies. That makes it so I remember to use it, and registers on the PC's tiny, reptile brains.
I found one feat recently that I immediately adopted as a "standard" feat for my evil cultist clerics. Its called Profane Lifeleech, from Complete Divine, and you spend two turn attempts to do 1d6 damage to every enemy in 30 feet, and healing that amount to the cleric. Its great, it spooks the PC's even though it doesn't really do that much, and its very flavorful.
For higher level Minion boosting, if you have a boss who can cast Unholy Aura, that will mess with your good PC's. Its an 8th level spell, though. Severla devils and demons can use it; I used it to great effect with a Marilith in 3.0 boosting up all the mooks defending her position.
In short, I look for one trick, and use it extensively in that encounter. The trick can come to identify the particular group of minions, making them distinct from other groups of minions, who have their own shticks.