Almost invariably, problems with mantle clocks are related to the chime. The clock sometimes won't strike the correct hour, the chimes have the wrong tone, the chime doesn't happen at the right time or the clock won't chime at all. Most of these issues can be easily fixed and don't involve delving into the movement's intricacies. One thing that can't be fixed is the melody -- if you don't like Westminster of Ave Maria, you're stuck.
Remove the minute hand and adjust it if the clock doesn't chime at the right time. Using pliers, remove the nut that holds the minute hand in place. Pull the hand straight off. Again, using the pliers, grip the bushing on the back of the hand and turn the clock hand forward or backward. This will adjust the hand on the face. You might have to experiment a bit. Re-attach the hand.
Grasp the hour hand and move it forwards or backwards to the correct hour for the chime if the clock doesn't strike the right hour. Then re-adjust the time on the dial by rotating the minute hand until the correct time displays.
If the chime doesn't happen at all, make sure the chime selection lever isn't in the silent position, check that all the packaging has been removed and the clock is wound. Another thing you can try if the clock doesn't chime is to lift all the hammers about an inch and place them back in their resting position.
Bend the hammer arms slightly in the middle if the tone is wrong. They are brass and can be bent. The hammers can strike the rods off center -- they can get out of alignment in a move, for example. Each hammer should rest about 1/8-inch from each rod or the coil or bell if that's what the clock has. Don't bend the chime rods, just the hammer arms.