Think fast: How much time did you spend on the subject line of your last email marketing campaign? This critical element too often is the last thing you consider before hitting "send." Yet, it's the first thing your recipients see in the inbox.

Sending an email marketing campaign with a lackluster subject line is like building a house without a front door. Maybe your recipients will walk around the house to find a back door, or try to crawl through a window. More likely, they'll just shrug and walk away.

Social networking puts the heat on the inbox

The competition for your readers' attention is fierce, and your subject headline is prime real estate. Besides personal email, opt-in messages, and the usual spam, every social network consumers belong to sends email notifications -- Facebook wall notes, Twitter follows, and LinkedIn invites, for example.

These emails probably have become your main competition, which means your subject lines have to work even harder now to get your customers' attention.

In this article, we'll take a look at seven of the most common blunders email marketers make when crafting their subject lines, as well as how to fix them. But first, let's look at a few general email subject-line best practices.

This screenshot of about 20 percent of my inbox shows you what your subject lines are up against:

A good email subject line anticipates and answers these questions:

• Who sent the email? Your "from" or sender line works with the subject line to make the message trustworthy. Any doubts about who sent the message or what it's about can doom your email to the trash or mark it as spam.
• What will I get if I open it? State the offer and what you're asking for or confirming right up front. "Hinty" subject lines ("You've just got to see this!") are total no-nos.
• Do I want this email, or is it spam? The subject line should clearly show that the email message is something valuable, trustworthy, requested, or anticipated.

This all must happen in a confined space, too. You think Twitter's 140-character limit is confining? Subject line writers have to do it in half that space.

That's a lot for a little one-liner in an inbox to bear, but the examples in this article should encourage you that it can be done. If you get stuck, think: "What will persuade my reader to act on this email message?"

The good news is that for every email subject line afflicted with the blues, there's a sure cure to make it sing a happier tune. Let's take a look at them.

1. Personalization run amok

Bungled personalization happens when people think the mail-merge function in their email list software will fool recipients into thinking a garden-variety commercial email is actually a personal message from a good friend.

If you don't require people to supply a first name, you end up with a subject line looking like this: "Hey, %namehere%, Special Deals Just for You!"

An easy fix might be to require at least a first name from everyone who registers for your email. However, personalization abuse occurs at a higher level, too.

At least three times a week, a school uniform supplier sends me emails like these: "New for Judy!" or "Don't wait, Judy!"

Judy is my mother, who placed a gift order for my sons and gave them my email address for updates. The list software merged the records and grafted my mom's name onto my email address. Women are supposed to become more like their mothers as they age, but this is too much.

The cure: Add a name field to your opt-in registration form for people who are signing up for email as part of a transaction.

The caveat: You might end up with a lot of "Mickey Mouses" on your list from subscribers who want to preserve their anonymity. Instead of relying on a name, write meaningful subject lines that speak to their interests instead of slapping a name on another boring subject line.

2. No "oomph" to the urgency

"Half Off Waxing and Tinting" said the subject line on an email from a salon/spa I like. Looked great! What it didn't tell me was that the offer was good until noon that day. By the time I opened the email, the offer was long gone.

The cure: State a time limit in your subject line if your offer has one. Just including your call-to-action should induce email subscribers to act fast, even if your offer doesn't have an end point.

A fix: "Today Only: 50% Off Waxing and Tinting."

3. Call-to-action is MIA

The subject line said, "Most likely to... " To what? No clue. Even after I opened it, I still didn't know, because the sender put all the information inside one large image.

Turns out it's a new product category that sounds kind of fun. But, I'd have to be a rabid fan of the upscale handbag manufacturer that sent the email to want to find out more.

Another subject line said "Expiration Notice." Was it for something that had expired or was about to? No, I just had to update a credit-card number.

The cure: Always tell the reader what you want him or her to do. The call-to-action doesn't have to be "Buy Now." It's the hook that will persuade the reader to act: an incentive, an urgency reminder, a price, a store opening.

A fix: "Expiration Notice: Update Your Credit Card" tells me what I need to do.

4. Call-to-action amputation

This email subject line has a lot going for it, but it makes one life-threatening error: "Kraft lunch ideas that don't break the bank. 6 meal ideas, $1 each."

Brand name? Check. Value proposition? Check. Call-to-action: Could end up lost if the subject line gets cut off in the inbox.

At 67 characters long, this subject line is at the outer edge of most default subject-line fields. The call-to-action (the $1 price tag) could disappear if the field cuts off the character count at 50.

And what's with the periods? At this length, each character counts.

The cure: Sacrifice some cleverness and save the call to action. Assume most inboxes will cut off subject lines at 60 to 70 characters. Make sure your critical information appears in that space.

Some email inboxes will reveal the cut-off characters if you mouse over them or allow users to extend the subject-line field. Don't count on subscribers to do either.

A fix: "From Kraft: $1 thrifty meal ideas." Result: 33 characters. The call-to-action is still at the end, but it's less likely to get chopped off.

Here's a good real-life example: "The Four-Bite Rule and other great weight loss tips."

In nine words and 51 spaces, you get a specific detail ("The Four-Bite Rule") and know there's more inside ("and other great weight loss tips").

5. "Same-old, same-old" syndrome

Is just seeing your company or brand name in the subject line enough to get your readers to open your email? Probably not, especially if they see the same subject line day after day. And don't they see your company in the From field?

When you publish daily, a standing headline might cut a few minutes off your work schedule, but it doesn't give readers a reason to look further.

"E! News Now September 22, 2009." That's a pretty bland headline for an email that's usually bursting with Hollywood gossip.

The cure: Use your top story or best offer to create the subject line. The inbox itself will provide the numbers.

A fix: "E! News Online: Fashion Police, Live from the Emmys 2009." Now I know there's something good, snarky, and timely to read.

6. Funky punctuation

News flash! Using "Free" in the subject line will not get you blocked automatically at major ISPs. However, disguising it with funky punctuation could, if you commit other email sins (broken code, DNS doubtfulness, giant images, etc.).

Even if you're not trying to fool the spam filters, using punctuation in ways the language never intended could also bring out the junk-mail hook.

Savvy email marketers have learned this. Amateurs haven't. You might be a niche or local retailer, but you don't have to look like one.

Some cringe-worthy examples:

"F*reed Shipping Today Only on All Cat Toys"

"F-R-E-E Health and Beauty Tips For You"

"Vegas is Calling!!!!!!"

Use punctuation sparingly in subject lines. It confuses more often than it clarifies.

"R&R Sale -- Fares start at $29*" (I read fine print to understand an offer, not a subject line.)

The cure: Is it free? Just say it. But use it strategically, not just to goose a blah offer. "Free" has a major impact -- unless everybody else in the inbox is using it too.

A fix: "Today Only: All Cat Toys Ship Free" (34 characters)

7. Cryptic subjects

Translation, please:

"NEW: Samsung 23" LCD $199... Sony 40" 1080p HDTV $749...Core 2 Duo Laptop w/ HD Graphics $579 & More New Deals"

Now, I know I said subject lines have to say a lot in a few characters, but you shouldn't have to know geek speak to understand what's going on. And enough with the ellipses!

The cure: Focus on a key deal or two in your email subject line and include more detail.

A fix: "New Deals: Samsung 23" LCD Monitor $199 plus Sony 40" HDTV $749 and more!" The "and more" could get cut off, but it won't detract from your other offers.

Conclusion: What brings on the blahs?

Bland email subject lines happen when you don't know what will make your readers leap into action. Testing, as you do on offers (I hope!), will help you learn this.