The right tool in the wrong hands can be a dangerous thing. Giving a chimpanzee a chain saw would not be a pretty picture. And putting Twitter hashtags in the hands of social marketers who were never really sure how to use them can be equally unattractive.

Boiled down, hashtags are for search and organization of tweets. A notch up from that, they can also be used as part of a marketing strategy.

In terms of search, if you’re in the organic apple business, you want anyone who searches “organic” on Twitter to see your posts about your apples. It’s keyword tactics not unlike web site keyword search tactics. So get a clear idea of what keywords are relevant for your tweet.

It’s reasonable to include #organic in your tweet. Is it fatal if you don’t hashtag the word? It depends on the person searching. If they search “organic,” your tweet’s going to come up even if you didn’t put the hashtag in front of it. If the searcher enters “#organic,” your tweet needs the hashtag. Err on the side of caution and hashtag it so it comes up no matter how the searcher enters it.

You’ll also want to hashtag it for the second big reason people hashtag, organization. You can follow a hashtag. So can the rest of the Twitterverse. If you’re that into organic munchies, you can set up a stream populated only with tweets hashtagged #organic. If you’ve established a hashtag for your brand, like #nobugsprayapples, you (and everyone else) can watch what people are tweeting about your company.

So what kind of hashtags should you include? They should be directly related to the core message of your tweet. Ancillary or very loosely-related hashtags = annoying. Hashtagging your brand makes sense. Hashtagging your core area of interest makes sense. Creating a specific event or campaign hashtag you want others to include and spread makes sense (the burden is on you to promote it and get it going).

Hashtagging nearly every word in the tweet is highly annoying. Far and away, the majority of hashtagged words in such tweets have no relevance, are not terms that would be searched, and are not terms needed for categorization. It looks desperate and spammy. Two is fine. One is better. And it is possible to tweet with --gasp-- no hashtags!

Make your hashtags as short as you can. In fact, if your brand’s name really is #nobugsprayapples, you’re burning up valuable, limited characters and risking the inability of others to retweet with added comments. Also try to narrow your topic hashtag down. You’ll find a lot of relevant users with #organic, but a lot of totally uninterested users with #food.

Just as you can join online forums and gain credibility and a reputation by contributing regularly to that forum, you can follow hashtagged topics and gain the same kind of credibility in your area of expertise. Don’t just parachute in for the occasional marketing message. And if you’re constantly retweeting one particular person, stop it. It’s kissing up and it’s obvious.

Which brings us to the king of hashtag annoyances, “hashjacking.” This is when you see what terms are hot and include them in your marketing tweet as a hashtag, even though it’s unrelated to your content. Justify it all you want, but #justinbieber has nothing to do with your organic apples.

Equally annoying, piggybacking on a popular event’s hashtag to tweet something not connected to the event. You’re only fostering ill will and mistrust toward your account from the people you’ve tricked into seeing your tweet. Lastly, don’t @ mention people just to make sure they see your tweet. If the tweet’s not for them or about them, it’s spammy.

What I haven’t covered is use of the hashtag for comedy’s sake. You’ll see this a lot and is a matter of personal taste. No one will search these hashtagged terms or need to categorize then, they’re just there for self-expression and laughs. Twitter is, after all, supposed to be fun.  What are some of your biggest Twitter pet peeves? #blogsovernow