I've spent the last couple of months reading blogs, following news letters, submitting domains and just generally learning all I can. Learning, not only by reading and research, but also by making mistakes. I once heard someone say "You can teach by being and example of what to do, or by being a warning of what not to do." While I strive for the former, I will share my experiences of the latter.
Like many inexperienced domainers, I spent a lot of time collecting hand registered domain names. Luckily, I had a few that had some value and I have at this point broken even with just two sales. So now, any income made from my remain domains will be profit. Some of the remaining domains I will renew at the end of the year if they haven't sold and others I will probably let drop. Any purchases I make from this point will be well researched and well thought out. I'm going to start to move from acquiring domains to developing a few that I have.
On that topic, there are some tools commonly used. Probably the most common is the Google Keyword Tool. By filtering on exact match, this tool allows you to see how often a certain phrase is searched in Google per month. Valuable not only to domainers, but to end users as well. A target of 1,000 monthly searches seems to be a minimum suggested standard, but if some cases you'll find a domain worth grabbing that is less than that.