"We have her for 13-14 months on average," says David Liu, CEO The Knot. The average US bride spends about $20,000 on wedding-related items. "It's a huge amount of expenditure in a concentrated time because it's a life event."

How can you make the most out of a revolving door customer base? Liu shared four specific tactics plus his plans for future expansion with us...

Tactic #1. Brand broadly across multiple media as a wide net

When you've only got a limited window of opportunity for life event consumers, you can't wait for them to stumble across you. Liu's team ceaselessly spreads a wide messaging net across multiple media so the brand will be top of mind the minute she gets engaged.

"To have a really powerful experience, it's important that you're able to touch target groups and reach them as many times as possible. Cross-platform integrated marketing is critical."

Luckily, The Knot is as much a publishing and content company as it is a shopping destination, so much of this brand messaging offline comes free (or even sometimes turns a profit) including:

-> Syndicated newspaper columns
-> TV specials co-produced with the Oxygen network
-> Printed books published and distributed via Random House
-> The Knot's twice annual national magazine
-> 18 regional magazine editions published four times a year

Aside from the big (unexpected) plug from The Apprentice this fall, The Knot's most effective offline outreach campaign was a viral direct mail campaign. Back in the 1990s, the site used to mail new members an ad-supported, binder-bound, wedding planning kit.

"It was a great organizational tool with helpful tips. We didn't tell brides they were going to get them. It became a great viral driver of traffic and membership. Brides would tell friends, 'Oh my god, the most amazing thing just came in the mail.' People started signing up in droves."

Now that the ad-economy has rebounded, Liu's team is considering restarting the program.

Online, the site has portal placement in AOL, MSN, and Yahoo! The site also gains a significant amount of organic search engine traffic from its wealth of constantly growing editorial content.

However, Liu says this heavy content approach isn't for everyone. "We've spoken to many retailers who want us to provide wedding content on their sites. But it's much more difficult to approach content when you're already known as a retailer. She's cynical that you're just trying to sell me products. We're viewed first as editorial media, so commerce is simply an added convenience."

Plus, neither search engines nor consumers are drawn to content that's not consistently updated and added to. You can't plant a library of evergreen wedding articles on your site and consider yourself done.

Tactic #2. Make online shopping easy

The Knot converts as many of its 2.1 million monthly unique visitors as possible into shoppers in three ways:

-> Using pop-ups as stable navigation tools. Instead of allowing advertisers to run promos, or running a variety of their own ads, The Knot's Web team sees pop-ups as another piece of the standard navigation bar.

"More intrusive advertising ones can become a turnoff after a while, and they didn't work when we tried to promote registration through them," notes Liu. "So now you get a consistent pop to promote accessories when you log in. We don't deviate from the content in those now. It's important to provide a consistent virtual space for members. It builds buying habits."

-> Search results that include both a small image and a bit of profile text. "Those little profiles can get anywhere from a 10-15% clickthrough rate." Lesson: don't rely on just images or text alone.

-> A thorough selection of shopping links -- even to offsite destinations. The Knot's home page invites visitors to check out brides' registered shopping lists across all major retailers (not just sites The Knot has a relationship with) in one easy search.

Thus the site becomes the search engine of choice for wedding-related purchases across the Web, some of which invariably will take place on The Knot itself.

Tactic #3. Register as many bride-visitors as possible

"Oh my god, I think we've tested everything from gating certain features to really pushing the value of services on them," says Liu.

Gating the entire site proved to be a big mistake. "If they can't preview or take a peek, there's no way they'll take the leap of faith and give you their information."

So the team turned their focus to providing interactive tools that seemed valuable enough to register for, including:

-> A personal wedding Web site

-> Heavily trafficked message boards

-> Week-by-week wedding countdown planning assistance

The tactics work. On the average month, roughly 108,000 visitors register as new members. The average member then returns to the site seven times a month for a total of 17 sessions during her lifetime.

Registered members have a higher ecommerce conversion rate during a visit than other visitors. The core group of frequent message board posters often convert at a slightly higher rate.

Tactic #4. Careful email campaigns

Just like maternity sites do, The Knot sends weekly personalized newsletters to each registered member based on how many weeks out she is from the big event. (Yes, there's also a series of post-wedding emails.)

Initially, email worked so well that the team was tempted to add in more and more campaigns. They discovered too much frequency could depress results. This was a particular problem in regions such as New York metro with loads of advertisers who also wanted to send out messages to the local list.

"We did a triage of outbound emails, and pulled back. Less is more," says Liu. Now each name gets a frequency cap, generally receiving no more than two-three emails per week, including her personal planning newsletter.

Advertisers who insist on running generic creative -- campaigns that either don't mention The Knot and/or aren't bridal specific -- invariably get the worst response rates. "You'd think that's intuitive," notes Liu. "You'd be shocked how many advertisers don't think about creative. They have their 20% off promo creative and they want to run it."

What works? "A retailer of beauty products wanted to launch a new line of cosmetics..." instead of allowing the retailer to run their standard promo, The Knot's email team talked the marketer into offering their members "a beauty kit for your big day."

Future plans:

With so much offline media presence, are The Knot brick and mortar stores the next logical step?

Liu says many retailers have approached him with partnership pitches for The Knot boutiques within a larger retail environment. But, he's hesitant to jump on board just yet. "It would be a fascinating experiment; but, gosh that's a whole world we are not schooled in."

Instead The Knot's current launch is online -- a site for newlyweds called The Nest. "If you ask them what they're planning on buying the first year of marriage, the spend becomes much larger than $20,000," crows Liu. "They're buying new cars, new homes..."

Sounds like there's plenty of room to grow.

Note: The Knot is a member of Shop.org, a forum for retailing online executives to share information, lessons-learned, new perspectives, insights and intelligence. More info at http://www.shop.org