I am in this situation where people inquire about my web development services asking for a meeting. The problem is they are not giving giving any details on work needed and their budget. I receive vague emails in the lines like "I need a web developer who is able to develop an e-commerce website for me, I see you are based in city X, can we meet up to discuss this?". If I simply reply explaining that they should start by sending me a short document explaining the work to be done, most of them just do not contact me again. The others would tell that is too difficult for them to put their ideas on a paper or the ideas are too sophisticated for emailing and require an eye-to-eye type of discussion (like their Google, Facebook + Twitter network idea).
In past, when I was in my first years a freelancer and desperate for new work, I would go to talk to every one of them. My experience was that these people
a) would have a tiny or absolutely no budget and were trying to con me into free work ("this will look good in your portfolio" or "we will pay you a lot if this project turns out well, however we think a legal agreement is not necessary")
b) were looking for a free consultant explaining basic internet business things to them, so they can teach themselves before finding a cheaper vendor.
Most of my work comes from larger agencies or referrals, therefore I will not starve ignoring these inquires. However I don't want to miss a single oppurtunity since some of them may turn out to be people with great ambitions with a budget to match them.
I don't see myself as a sales representative. If people agree to work on my terms from the very beginning, like making a short spec before going into a live discussion, most of the time the whole thing turns out well and everybody is happy in the end. However, clients like that are rare.
I would like to ask how do you effectively handle these potential clients in your freelance business ?