I find mage secrets to be the hardest to play around. It helps they don't tend to run them all, so if you see Duplicate you can guess there are no Ice Blocks, but there probably will be Mirror Entity. But with Hunter you can play a minion, attack face and attack a minion, that will trigger all the secrets, so if you attack face and nothing happens it's most like Snake, you can play super safe by checking for Snipe haha. There are so many ways to trigger mage secrets though, they feel way harder to play around.
When a mage plays a secret I have to think what it may be. Counter, mirror, duplicate, spellbender, or vaporize are the only ones I really care about unless it is near end game and then I care about ice block. The ice shield is ignorable.
So I have to try and assume the worst based off what I want to play in my hand. So if I have a big minion I want to play, I will play something crappy first if I can to deal with the mirror. If I a spell I want to use, I'll try to use a spell that I can "lose" to the counter if it isn't a mirror. If I think it's a duplicate I try to take out the weakest minion first if possible. So I have to think around the mage secrets a bit more.
Hunter secrets I have to think around some as well. But, they are easier to predict than the mage ones. If the hunter has a clear board and I have something on the board it is either an ice trap, explosive trap, or possibly misdirection. So I play accordingly to that. If my board is clear it is probably a snipe. The snake trap is ignorable for the most part.
Paladin secrets are pretty much Avenge, Noble Sacrifice, and Eye for an eye. Everything else is ignorable. However, the only two you can play around is Noble Sacrifice or Eye for an Eye, which means it's not hard to predict or play around paladin secrets.