Many Twitter accounts are not run by real people. They are automated programs called bots. And some of them are spammers.

There are bots that provide useful information. However, most bots are spewing out tweets from other people and other sources that are not on target for your Twitter business goals. They clog up your Twitter stream and don’t provide any business value.

You may not have known you were following a bot. Bots gain an audience by following many people and taking advantage of people who automatically follow back.

In general, it’s better not to follow automatically everyone who follows you if you want to avoid having your Twitter stream fill up with garbage.
So how can you spot a bot or spammer or someone whom you should not follow back?

Here are a few suggestions:

Don’t follow people with an egg picture. If they haven’t bothered to upload a real profile picture, chances are they are not going to say anything worth hearing.
Check their numbers. An account that follows many people but has only a few followers is probably a spammer.
Review their tweets. Are they all retweets or quotes? Did they send the exact tweet to many users over a very short time? It’s probably a bot.
They say it’s a bot in their bio. Yes, some bots will tell you they are bots in their bio.
No favorite tweets or lists. A bot or spammer doesn’t mark tweets as favorites or create lists.