I have used a ring sling very successfully, and the only piece of advice i would give you is to have an extra set of hands when you are trying to figure everything out and once babe is in the sling, start moving immediately, because some babies fuss when they are first in the sling, and parents fret that the babe doesnt like ti and the thing is that babe needs to be moving to adjust.
Anyway, one site i would recommend is this one, it seems to have definite step by step instructions with pics. Also in the same site there is this one. The ones I used the most with my charge at 4-10mos was the hip straddle and if she was asleep i would change her position to the snuggle hold and she would sleep better and be more content.
Let me know how it goes!
edited to add: instead of having the padded end resting in between my shoulder and my neck i would recommend putting the padded end on the shoulder(cupping it) and have th rest of the fabric spread very wide extending to my neck and halfway down my arm (make sure to put is on your non dominant arm so that you can support and comfort as needed).
If you need any more advice or pics, I am sure I can borrow someones baby for a few moments or use a doll.