If you are really ambitious you can create your own community around your web site. By participating online you are getting your name out in the community, staying current with all of the latest developments, and making crucial contacts that can include book reviewers, magazine editors, book editors and the real gurus of the technology. Many authors have come to prominence on the newsgroups, particularly in the web scripting and programming area. It's important to be helpful, answer questions, and make yourself available, without pushing your books too obviously or obnoxiously. If you spam the newsgroups or forums it won't serve you in the long run.
Many publishers look first for trainers or consultants to author books on certain topics.
To become known as an expert in the community, you need to stay current with what is happening with the technology. It's good to diversify if you possibly can, if you concentrate only on writing books, you can become out of touch with the latest advances. Consulting will keep you on the cutting edge. Also, if you're lucky, the company or companies for which you consult will want to buy a copy of your book for the entire staff. Trade Shows Trade Shows are a fantastic place to promote your book.