I try intentionally to make myself unreadable. I watch and observe at the beginning of tournaments and start to figure out who knows what they are doing from those who are winging it. Who has a pattern with their bet sizing and bet timing with relation to their hand strength. A very important thing I look for is strength of their hand cards in relation to their position to act.
One thing that makes a player very difficult to read is the one who will develop a different strategy for each player at the table.
As for freerolls , I just play by the book and hope for the best results.