As described on pages 206-207, Jack grammar is almost LL(0). The 0 part means that the current token (the thing you're "looking" at at the moment) is enough to know how to choose between the alternatives.
The only exception is the parsing of expressions, where you'll need to do a single look ahead. What does that mean? It means that you need to peek at next token to see what it is so you can dispatch correctly.