I'm seeing way to many people making Double battle sets without including Protect. Here is a little history lesson for Single battlers.
ALWAYS USE PROTECT!
In Double Battles, the uses of Protect are almost always there, staring you in the face. Predicting a double attack on one of your pokemon, but you don't want to switch? Protect. Want to stall out a turn of Trick Room? Protect. Basically, if it isn't super fast, absolutely needs 4 moves, or has a Prankster Substitute, you need Protect. There are some exceptions, like Choiced pokemon, which usually are bad in Doubles, but most of the time, just put Protect as your first move and work from there on your pokemon's moves.
"We must treasure these (Unown), since they are us at our very core...
ALSO, DID YOU KNOW THAT YOU CAN MAKE WORDS OUT OF THEM? THAT'S PRETTY COOL!!!!!!!!"