There are lots of things that a dog can pull: you (running or on skis, known as canicross and skijouring), a sled, or some kind of wheeled device which you need if you don't have snow.
In October 2008 we decided to start with a dog scooter (you can also run dogs hooked up to a bike). As always, we read a lot of stuff (dogscooter.com and the Yahoo Dog Powered Sports group) before deciding on a scooter. Our choice was a Pawtrekker, based on comments and reviews. After talking with Colin at Pawtrekker in Canada, we decided on the FreeTrail model (no longer available).
The Pawtrekker is specially designed and built for running dogs. The FreeTrail has disk brakes, front and back -- essential for trying to stop the team suspension front and back to ease some of the bumps; and a brush bow, to attach the dogs and minimize the chance that the gangline gets wrapped around the front wheel. We picked orange for visibility -- no one was running dogs on trails around Pittsburgh, so we wanted to be seen.
We got some basic gear -- a good helmet and ganglines (we picked a ski helmet -- we want warmth for winter, and bike helmets focus on cooling -- we've since upgraded to a MIPS technology helmet for better protection http://mipshelmet.com/home). We already had some harnesses. So we were set.
It's not hard to balance the scooter, once the dogs are pulling. You do have to kick when they aren't pulling (scooters are also called kick bikes) or to help when the going gets too tough. With the suspension, the Freetrail is a little higher off the ground, so it makes kicking a bit more work. Some folks complain that the footboard is small, and it is smaller than on other scooters. You can't stand with your feet side-by-side, but you quickly adjust, especially if you are starting out slow like we were with Rubi and Denali.
The Pawtrekker has a couple drawbacks -- there is no easy way to carry water for the dogs, or poop (we have to pickup on the trails, and dogs tend to go when they start to run). Newer models fix this. Otherwise, it's just normal maintenance.
The FreeTrail also has quick releases all around, so it can be easily folded and put into the back of an SUV, but we soon decided that was too much work, and too messy when it was raining or when the dogs found mud (whenever they can). The scooter doesn't have fenders, so you can get pretty muddy on a wet trail.
We decided to get a bike rack. The problem was that with the scooter's added suspension, the Freetrail has a longer wheel base than a regular bike, so it won't fit on a regular bike rack (unless you hang it upside down). We did find a Saris Cycleon at our local bike shop that they got in by mistake, and were willing to sell it at cost. With a bungee, it just fits, and we can load/unload the scooter in just a few seconds. We've since modified the bike rack to remove one set of hardware, and put in eye bolts, so we can attach the dogs while we are setting up or packing up.
So we were off, running dogs, doing short runs, typically one mile (we keep a log where we record what we do every time out in a spreadsheet). Still figuring it all out on our own, but having fun.
After 3 years and over 400 miles, the front disc on the brakes warped. The bike shop tried to repair it, but hauling it around on the back of the Highlander in slop and road salt had corroded the bolts. Net effect was a new set of hubs, spokes and new brakes. While the brakes that come standard on the Pawtrekker are OK, the new one are really nice and good enough to stop the team in an emergency. And they don't squeak -- on the trail all you want to hear is dog foot falls, dog's breathing and either runners on snow or wheels on trail -- driving a team is an incredibly quite and peaceful experience.