It is very important to find if you smell bad. While it seems easy, to actually figure out if bad odor comes from you is a difficult thing to figure out.
Check your clothes when you remove them
Your clothes are the most important tool to identify if you smell bad. Smell them including underwear and they will tell a lot about you.
Socks will tell you clearly if your feet stink.
Check areas like underarms or your chest
This will straightaway tell you if you smell bad. This will not be possible for all parts of the body e.g. your hair.
How to tell if your breath smells bad
To figure if you have a bad breath, hold your hand against mouth and puff. Your nose should be able to pick any smell that comes from your mouth. Do it at a time when you have not brushed just or just after waking up or just after having food. These will affect the smell so you should avoid them.
Another way is to lick the back of the wrist for some time. And smell it to figure out.
How to tell if your hair smells
Run your fingers on your scalp a few times and ensure you reach the root of the hair. Smell them to know what your hair smells like.
Ask someone close
If nothing else works or you are not sure the best way is to ask someone who is close to you and whom you meet regularly. This is the best method.
Remember you can figure out most of the smell from armpits or feet. But if you suffer from fecal or musty body odor you will not be able to figure out by yourself if you smell bad. The only way you can figure out is if you enter a room again after leaving it. Hence asking someone is the best option.