I have hiked with partners over the years that do from 1 mph to trail running....I'd say most end up doing 2 mph or so with photo taking, "enjoying the view" (ie..breathers), getting snacks, etc. That is a very comfortable pace to hold day after day.

The biggest thing is not overdoing it right out of the gate. I learned long ago that I hate people who go running up the trail immediately. I prefer to amble and warm up then get to speed (less injuries that way!) but also with newbies one keeps the miles down. While an experienced hiker is prepared for long miles/hard elevation it can be overwhelming. So if it is someone who hasn't come with us before we keep it under 10 miles - no death marches. I do have a couple friends who would hike all day without stopping (I will do this on death marches when it gets close to 20 miles) so I make sure we DO stop and relax every hour. After all it needs to be fun. The torture is for later, when you willingly sign up for it

Anyways, don't worry about your friend being in better shape. But DO take the time to start walking on a regular basis. Get your shoes of choice worn in a bit (avoid blisters that way!) and to help develop your legs. Walk with a pack on - even a daypack to get used to it.

And do get a couple books out of the library on navigation It is easier than it looks and can be fun! Research the area he wants to take you to - look up online photos, trip reports, etc - it will get you excited to go!

But the best advice I can give you? Don't let yourself get stressed if you are behind them - that only leaves you feeling worse. Instead...smile, breathe deeply and walk at your pace. With a good map and skills you will be OK.