what are 3 characteristics that tom displays at the beginning of the novel/

I guess that you can say Tom is a dynamic character. By the end of the novel he certainly matures yet he maintains some of his childhood charm. Much of Tom’s early personality can be seen in early chapters.

Tom is mischievous- he escapes his aunt Polly using the old "look over there trick". He skips school to go swimming.....

Tom can be a fighter- (scrappy) In Ch. 1 Tom exchanges insults with a new boy and ends up fighting him.

Tom is clever in a sneaky sort of way- In Chapter 2 Tom attempts to trade Jim a marble to help with his chores (whitewash fence).