I walked the Camino in April & May of 2009, I did not use a tour company. I planned it all in 2 weeks. I bought some books, studied the online routes and decide where I would start from. The Camino is a place of brother/sisterhood. It is safe and contemplative. I was a 47 year old mother of 3 and out of shape. I took way more than I needed and it was the experience of a lifetime. Pick where you want to start, get a hotel for a few days ahead of your start date, ask other pilgrims at cafes and restaurants or outside the alberges for advice. This is what I did and it was great. You really don't ever need to use a tour guide. But, please be respectful and try your best to learn some Spanish before you go, have a basic command of the language at least, carry a pocket dictionary and use your manners. Also carry your own roll of toilet paper, have good insurance and do not, do not drink out of the fountains no matter what they say. I met 3 people, differernt locals that ended up with parasites and giardia! I carried a camel back in my pack and refilled with bottled water as needed. You don't need half of what they say, you arent traveling in the great wilderness, there is civilization around. Do carry duct tape wrapped around a small pencil, a paracord bracelet and a headlamp.
If you get sick do not rely on the Alberges to help. I had to help several people and the alberges, both the religious and the common were of absolutely no help. The sick and injured I was with were shut out of the alberges even for a single night, we actually ended up sleeping in a neighbors car because there wasn't a hotel arround. That is my only word of caution.
I made a lifelong friend and met people from almost every continent, I started in Roncesvalles and ended in Compostella, with an added trip to Finisterra, it was the right thiing to do. Eat the food, meet the people, take a few days to visit a town or city that calls to you. Don't be a power walker, if you do you just might miss sitting in Hemingways cabin.
Buen Camino,
Amri