Walk as light as you can, safely. I found 2 T shirts, 2 combi lightweight trousers 3 pairs of socks and 3 pairs of pants were enough. I also had a nice clean shirt for the evenings in the Refuges, just to make me feel human. A fleece is a must as the evenings do get alittle chilly.

MSR stoves are the way to go, fuel for Gas is rare, we found a petrol station at Huesca while we were waitng for the connecting bus.

Para cord and pegs came in really handy for a washing line, even in barcelona.

Strong water proof boots are needed and good sandals for crossing streams. I broke both our walking sticks, but I think they would have come in handy if I hadn't.

Make sure your sleeping bag is in a sealable water proof bag, you do have to cross streams and in you fall in, you could be in for a cold night.

A sun hat is a must, but so is a woollen hat and gloves.

Basically carry everything you need to keep alive if you were walking in the desert, or in the snow.