What is a writer's platform?
Your writer's platform is basically the group of activities you engage in that get your name and work noticed by the public. It's everything you do to build your brand.
Why Build One?
If you are currently unpublished, the fact that you are building a platform and marketing yourself looks great to publishers. Publishers love authors who are willing to get out there and market themselves. The fact that you're already doing so proves that you're the kind of writer they want to get behind.
If you're already published, your publisher undoubtedly expects that you will get moving on your platform as soon as possible.
When to Start?
Some professional authors have a carefully crafted public face.
A simpler way is to just be yourself and tends to be preferred because fake personas are difficult to maintain, and the public is good at identifying fake marketing.
Building a brand can be fun, rewarding work that fits in well with the writing life and gives a social balance to what can be a solitary occupation. But it is hard work and time consuming - no one can do it for you! Everyone starts off unsure of the technology, but it can be mastered.
What do I need to do?
Website/Blog: Starting a website or blog is an easy, cheap way to launch your platform. You can be set-up with a basic blog literally in minutes.
Social Media: Once you've got your blog up and running, the next step is to start using some social media tools to help drive traffic to the blog. The two main tools for this at the moment are Twitter and Facebook. Start with these, and once you get comfortable you can evaluate other newer tools as they appear.
Public Speaking: Speaking at writer's groups can help you build your brand, and meet other writers.
Teaching: Another great way to get your name known, and to make a bit of extra cash.