I think there’s one principle that rules all:

“Create value for others.”

It’s the greatest sales mantra to date, in my opinion.

Nifty web tools helps create value for others. And to your point, so does the content. It all works together.

So, here’s a question to add … how can you best create value for others with your content? Or you can ask, what’s the best form of self-promotion?

I like Brendan Florez’s (CEO of Social Charm) answer:

Let’s say you’re trying to convince a potential customer/employer/investor to begin a relationship with you. There are only three ways to do it, and they are not equally effective. From worst to best, here they are:

1. Tell them how great you are.
This is the least effective method, but it’s better than nothing. The key here is to be honest and not come across as trying too hard to impress. When an older gentleman asked Bono what he did for a living, the rock star said, “I’m a musician.” Don’t be shy about your accomplishments, but don’t oversell yourself either.

2. Have others tell them how great you are.
Marketers have a name for this – social proof. If you and your customer have a mutual friend, ask that friend to put in a good word for you. If not, think about who else your customer might consider asking about you, and seek to make a good impression.

3. Show them how great you are.
Nothing’s more powerful than a customer witnessing your expertise first hand. If you’re a marketer, offer some quick marketing advice for a problem they have. If you’re a property manager, give them a tour of your places and show them the financials. Find a way to directly demonstrate your skill, and your chances go way up.
The real power of these techniques comes when you do them together. Spend the majority of your time focused on #2 and #3, and #1 will take care of itself.