LinkedIn is an extremely powerful networking tool. You know why: You can get more leads and referrals. You can find awesome groups. You can optimize your LinkedIn profile so other people can more easily find you. And you can, if you choose, use the power of LinkedIn to irritate the living crap out of other people.

Here are five things you should never do on LinkedIn:

1. You want to connect... but don't tell me why. "I'd like to add you to my professional network." I know it's there for a reason, but still, is using the auto-generated LinkedIn connection text really the best you can do if you really want to connect with someone?

Delete the generic message and take a few seconds to say how you know the person you with to connect with. Or to say what you have in common. Or say something complimentary. Unless you're just trying to pad your numbers, you probably have a good reason for wanting to connect, so say what that reason is. It only takes a second.

And besides: making real connections starts with the word "real." So be real.

But, okay. Maybe you really are too busy. Fine. Using generic message isn't the worst thing you can do, unless you follow it up with this:

2. You connect and immediately ask for something. Say I don't know you and you ask to connect. I almost always accept because many people want to connect just so they can keep up with what I write. (And I'm more than cool with that.)

But say you connect and immediately want something. Not something simple. Something major. You ask for a referral to someone your new connection knows--even though your new connection doesn't actually know you. Or you ask for help in landing a job. Or you ask for business. Or...You get the point.

If you wouldn't want up to a stranger on the street and make the request, don't make that request of someone on LinkedIn who you've just "met." Sure, it's easier since you're not face and you get to hide behind your computer, but it's still tacky.

3. You ask people who don't know your work to provide recommendations. Sure, I could say something generic, but what's the point? People should recommend you because they want to, not because you make them feel they should. Don't put people in a position to either have to ignore your request or to write something bland, superficial, and insincere.

Either way, they lose. And ultimately so do you.

4. You endorse people once a week in order to get their attention. I'm not sure how valuable Skills & Endorsements are. But they exist, and lots of people make them. Once they do, the person endorsed gets notified. So far so good. Unless you endorse the same person, say, once a week. For weeks. And months. Picking a new skill each time.

Clearly you're not providing sincere recognition of her skill or experience--you're trying to make her notice you. Do it twice and hey, no problem. Maybe you realized she does have additional skills. Great. And maybe that does help her remember you.

Do it three times, or ten times, and that will definitely help people remember you--and not in a good way.

5. You use a photo that shows you in an unbelievably good light. Think about people you know. Check out their photos on LinkedIn. While a number of images seem cropped from a photo at a party, most of them look pretty good, right? Now do a quick image search.

Do the photos you find look like the same person?

Not quite, and that disconnect is often more than a little jarring. The Hugh Jackman you see in the profile photo turns out to look more like, say, me. (Now that's a jarring disconnect.) Of course you should try to look good in your photos. Research clearly shows people want to do business with attractive people.

But don't try to look too good, because people also want to do business with real people. Plus, someday you may actually meet your customers in person... and then they find out you're not quite as handsome, or trim, or young, and definitely not the focused-yet-sensitive-artist-with-a-mischievous-smile your photos make you seem.

That's my five. What would you add to the list?