I looove biking with Traveler and have started Didgie on really short bike rides. Some of my favorite memories are on bike rides!
As far as running on pavement goes I hope someone else can help you since I pretty much do none of it. I ride either next to the curb or the edge of the sidewalk so they can run in the grass or I'm on bike paths that aren't paved.
I would start slow definitely, though how slow depends on her physical condition. Traveler I started at about a mile. Didgie is doing down one street and back since she's a baby. I also always try to vary the pace, some fast bursts, some trotting and so on. Sometimes I'll do a really fast three mile bikeride other times I'll do a more leisurely 7 mile bike ride.
One thing I do try really hard to do, especially in the longer ones is having a break part way through where we're doing something else. In the summer it's typically fetch in a pond/lake. During colder times I do some fetch in a field or up a hill. Sometimes I'll go for a short hike through some place. Just something to break it up.
For getting her used to it I would maybe if she's food driven try and treat her for staying near while you're on it. But, to be honest my typical method is the cold turkey, lets GO! method
I get on the bike, I ride and I let them figure out that we can RUUUNN! Though with Didgie I'm also treating while doing it. She the first time said "WEE!" And tried to jump into my arms.
As far as the leash goes I don't use any contraption, they make me nervous. I like having the option of letting go of the leash if need be (And I've had to do it before), letting them out farther, reeling them in, switching sides etc. So all I do is let the leash handle go through the bike handle and then loop it around once so my hand is resting on it. That way I can grab and tighten if I need to or let go if I need to. So far it's worked well for me!