Does it matter which hand does the circling?
Yes, your dominant hand should always be the one making the circular motion. Your non-dominant hand acts as the stationary base.
How do I sign 'next year' or 'last year'?
For 'next year,' the dominant fist starts on the base hand and points forward. For 'last year,' the dominant hand starts on the base hand and points backward over your shoulder, showing time moving into the past.
Do I use this sign when talking about my age?
Usually, no. In ASL, age is typically expressed using a specific 'age' sign where you pull the number down from your chin, rather than signing the number and then the word 'years.'