I have used one for years - long before I needed someone to do my taxes :) People have a misconception that planners are only for the wealthy, but IMO, they can help anyone.
I like to go with an established company, not an individual, because I know that there is an establishment there and checks and balances, and no one can run off with my funds. Over the years, I've switched around a bit, but this is mostly due to the personality of the person I was working with. Even though I don't have a lot of $, I think I deserve good customer service, and when I didn't get that, I switched.
If you do go with a big company, the fees are pretty similar among them (my experience is with Merril Lynch, AmEx, and Hefren Tillotsen, of those, I thought AmEx was the least useful, the other two were better).
The best thing to do is really to call the office of a company that has a good reputation and is convenient for you. Describe what you are looking for - you need a comprehensive plan and how you would characterize your assets/lifestyle (eg, younger and middle class and looking to grow your assets OR upper class and your concerns include tax planning and protecting your assets OR whatever). They may have some questions, and then they can usually recommend a specific planner in their office that sees the kind of client that you are.
First visits should always be free so that you can evaluate them, see if it is someone you think you can work with, and who seems competent when you talk to him/her. If you stay with them beyond the initial visit, they will charge a fee based on the assets in your account.
ETA: yes, some others bring up a good point. Ask how long the planner has been with the current company. I too got a 'jumper' at one point - it seems to be common in the industry. I moved funds with him twice, and when he told us he was going to a 3rd company in 5 years and asked us to move with him, we moved - but not with him. We went with our current person, who has been with the same firm for many years. And have been much happier.