In reply to Gav Parker:
I started out with the Ramblers leading walks, I've learned a lot from them over the years, not only about building on a more broader experience in the group management skills but about the environment, wildlife & flora, and have made some good friends too. Some group members might be involved within the environmental side of things and they are a pool of knowledge.
Where as you would probably do a lot more lowland or hill and moorland leading with the Ramblers, its good experience working with the group side of things. Leading groups who still want to get into the hills but like shorter walks than the norm, is a good skill to build on, because you work much more closely with the reccing side, choosing the appropriate route on the fringes of the uplands, but occasionally going a little bit into the uplands and not striding out to the tops; it's when that type of walking suits a group I find interesting as you tailor your route specifically. Quite often the route is very interesting and challenging from a navigational aspect too.
Speaking to locals/farmers about things you find interesting on route is a good idea as you'll probably be asked about the things you pass when you lead your walk, the more information you can provide will make the experience more interesting for all of you.
Walking groups are always keen to have new leaders, especially younger leaders, walking groups are conscious that they need to recruit new younger members, you won't have a problem joining and leading, I found the most important thing was to be realistic route wise with the people I was going to lead for. Getting to know what they like before hand will give you a better idea on what to give from your leading.
All the best
Jason