Casement:

• ensure that the tracks are clean, apply a silicone base lubricant
• check to see that the locks are in the open position before closing
• if you have left your window open for most of the summer you may have to pull in on the top of the sash for the locks to engage, this is normal and the sash will go back to its normal shape when kept in the lock position for a while

Vertical slider:

• check to see if any debris is down in the interlock. To check this, open window up at least 6" and tilt in, you will then be able to inspect where the sash meets in the centre of the window
• ensure that the locks are in the open position before closing window
• ensure that the pivot bars are in the shoes, these pivot bars are located at the bottom of the bottom sash and are engaged into the shoes that slide in the balance chamber steel doors - inspect bottom door sweep to make sure that it is adjusted, up too high and you will have air or water leak, to low and it will bind up on the sill crown making it hard to operate the door and will wear out the fins.   

Door:

Check to see that the striker plate (this is part of the lock set) on the jamb is set correctly. If you have to push on the door slab to close, the striker should be moved towards the interior. If the door feels loose when in the closed position, then the reverse is required.