If your going to use your fireplace or wood burning stove. Have it swept every cord 4'x4'x8') of wood you burn.  Also make sure before you use it you get the whole system inspected to make sure it is properly installed, all clearances are met and it is safe to use.

This is the time to get your chimneys swept out.  The lows at night are dropping to low thirty's.  If your planing on using your fireplace or wood burning stove this winter, get it swept out while it is still warm during the day.  This will save you money.  When it gets colder outside more and more people start calling.  Then it starts to get extremely busy and prices for sweeps go up.