There's a lot of debate on many forums about whether Twitter is really useful as a marketing tool or if it simply contributes to the level of social distraction that characterizes a lot of Web 2.0 applications.
I use Twitter in my marketing and I've found that the more well known a person is before using Twitter, the more followers they amass quickly as others want to connect with their celebrity. However, all is not lost for those of us who are working to become established and who want to use Twitter as an effective marketing channel.
A good example of how to integrate Twitter with what you're already doing is blog promotion. I use WordPress for one of my blogs. There is functionality built into WordPress to send a Twitter update to your Twitter account each time make a new post. If your posts have good titles, the fundamentals of successful marketing will kick in and other individuals who are using search features of Twitter applications will find your Twitter post and often decide to follow you.
I've had this happen personally when mentioning a famous person's book or product and then being pleasantly surprised when that person has decided to follow me. Many times, those who are following famous people will also choose the follow the people that their famous people are following so I gain more traffic through the positive association.
The same automatic integration applies with those who are using Squidoo. You can opt to post a Twitter about any updates you've made to your Squidoo lenses. The key with any of this is to make the updates meaningful and interesting enough to either get people to visit your site or to decide to follow you or both.
The real secret to Twitter is using powerful developer applications that enhance its functionality. Tweetlater is a prime example. Tweetlater allows you to set up functionality with Twitter where you can automatically follow anyone who follows you in addition to sending them a welcome message from you as soon as they start to follow you. My welcome message thanks the individual for following me and encourages them to check out my forum for other great information.
You can also use Tweelater to schedule Twitter postings for the future and establish an RSS scheduled Twitter feed to make special announcements or to keep your Twitter account going while you're away or focused on other activities–it's kind of like a Twitter autoresponder that limits messages to 140 characters for ease of reading and guaranteed delivery.
Twitter is quick, easy and effective in terms of providing you with additional exposure and visibility or for just keeping your customers, friends and followers up to date on your latest endeavors. The key is to strike the right balance between daily ramblings that provide personality and social interest with solid awareness about key posts or product announcements that are important to your following audience.