UV Unwrapping complex organic shapes

I have so far managed to avoid needing to be very good at UV unwrapping, however I have now decided that I want to be able to do this for any object in one of my scenes (box mapping and other simple projections had done the job on most cases, and and easy shapes could be UV unwrapped with my limited knowledge).

If I have a complex organic shape, lets say for example something like a tree. How do you go about that? I tried to UV unwrap an older model that I had modified for practice, but this seems to be particularly difficult with my current understanding. Should I create separate UVs for all the branches and then try and re-attach them afterwards? Should I try some elaborate seam that makes it possible to “squash” the whole tree into one UV island? Or something else?

Also, I have been using decimate and subdivision in order to create a model that I can UV unwrap. This might not be helping. In cases where it is not working well like this, should I be creating a low poly version of my model and then subdiv + shrink wrap? I will need to read up on how best to do that too…(any tips welcome!).

one way to do it is: simply unwrap the mesh, create a new big texture file, go into paint mode, use the textures you were using as brushes, and paint your model as you like.
This way your final texture will be kind of chaotic but the render will know well how to deal with it. (its a bit as sculptris works, but its very straigthforward)

Thanks, I will give this a try!