what are the suspense throughout the book?

We wonder throughout the book whether George and Lennie will ever get the farm, and when/how Lennie will get into trouble again.

Other smaller examples of suspense occur after Lennie crushes Curley's hand: will he be fired? Also when Lennie is talking to Curley's wife in the barn: will Curley catach them together? Will Lennie hurt her?

The biggest suspense is what will happen after Lennie runs away. Who will find him first--George or Curley's gang?

There. Develop some of those ideas.