Jennifer,
I don't suggest giving away your time for a trial period. I believe that your testimonials, internet presence, expertise and the information you provide in the consultation should be enough to prove you can do the job well. If you say you can do it, they must trust that you can. Giving away your time IMO cheapens your services. Although, I know others will disagree.
Do you ask an attorney to work for free while you determine if his services meet his needs? The same should be honored as you are a business owner as well.
Any number of things can factor into why the deal is not closing and some of them may not be you. There will always be clients that change their minds and truly that is a gift because anyone who falls into the 'black hole' is not your ideal client. In fact, they may be a problem in the future.
I would start by evaluating your consultation that you give to each client. Do you have a new client welcome packet? I send this ahead of the consultation so that they have an idea of my policies and procedures. This eliminates any surprises during the call.
There is plenty to absorb on the internet about overcoming objections. So keyword this and see if there are any tips you can use. Here's one such article
http://sbinformation.about.com/od/sa...objections.htm
I like to work with people who see my services as an investment as opposed to an expense and I use that word 'investment' in the consultation. So look at the words you are using during the call.
Find out what it is that they need help with. They are coming to you for solutions. Can yo provide those solutions without giving away the store?
Do you research these clients on line beforehand and notice issues that you can help them with. For example, if they use social media but only have 100 subscribers can you suggest and explain what social media can do for their business and offer ways to increase their subscriber-ship? (Just an example, I know you are in legal.)
Just keep going with whatever you are doing. Fill the marketing funnel with as many interested parties that you can. Those that come out the funnel will be those you work with.
Janine