In reply to compost:
Yes, 1/2/3 - you need to be at least as fit as the person who you're running FOR - remember, you'll have more kit as one assumes you'll help with the muleing. Good thing is, you only have to run that leg so you can go a bit deeper than normal
Leg 2 is great if you're confident naving in the dark and it's got some great running on it. Be worth figuring out which way they want to come down off Dollywaggon before you start the round, same as the route up on Clough Head (the correct answer is a directissima of course)
As Nic said, you need to know what your role is - or are you all the roles if you're the only pacer? Be prepared to sort your own shit out. If you're in a group and you're the slowest, drop out, get yourself off the hill. It's not your round - its theirs. If it all goes to crap, you need to not be the weak link.
However, when it all comes together, and you get someone round in the time they want, or just that little bit quicker but without wasting them.... it's a great feeling.