Brush your teeth after every meal. Also rinse your mouth after
every meal to remove food particles sticking in your teeth.
Try to clean your tongue with tongue cleaner while brushing your
teeth.
Try to drink plenty of water to avoid making your mouth dry.
This will also help in flushing out bacteria present in our mouth.
Use good mouth wash which can kill bacteria and fights bad
breath.
Keep a check on your diet as specific foods can cause bad smell.
Garlic, onions and fish are known to cause bad breath and try to
reduce its intake.
Check your dentist regularly for gum disease which is also one of
the root cause of bad breath.
Hope this helps.