When in any date field it is possible to use short cut keys:

t - today

w - beginning of week

k - end of week

m - beginning of month

h - end of month

y - beginning of year

r - end of year

When in any money value field - there is a built in calculator.

Additional Setting Tips
 
Under preferences I recommend these settings.
 
Show the Lowest sub account only: this setting allows you to more effectively use sub accounts by hiding the name of the parent account. (This feature can only be used if you have account numbers assigned to your accounts.)
 
Required accounts: this forces the user to code every transaction to an account.
 
Use class tracking: this setting enables class (activity) tracking in the company file.
 
Prompt to assign classes: this setting activates a message reminding you that the Class field has not been used in a transaction. (This is very important when using classes.)
 
Use audit trail: this setting is important for providing back-up for transactions.