The only real way to tell if your chimney needs cleaned is to look inside the chimney itself with a flashlight and check for the thickness of creosote buildup.
If you notice a lot of creosote build up especially if it's 1/4"" thick or thicker then you should have the chimney cleaned or clean it using a chimney cleaning brush.
Creosote that is 1/4" thick or more will start a chimney fire soon after lighting the fireplace or wood stove.
With a wood stove you may need to get up onto the roof and check the chimney since it's hard to see up the chimney of a wood stove.
Chimneys need cleaned every 1 to 2 years depending on how often you use the fireplace or wood stove and if in doubt have it checked and cleaned before it starts a chimney fire which can cause you to lose your life and your house.