I highly recommend a bike attachment. I started my dog biking without one, but I hooked him up to his prong. Not the best way to go, but the prong barely phases him as it is and it allowed me very good control. I also am VERY vigilant and if I see something that could possibly get him going, I warn him with a stern "leave it." We do go speedily enough that he's too focused on trotting/running to do much else. If I have to slow down, I "whooooooooaaaaa" him with a low, slow voice and if I have to, I'll check him lightly with the prong. Yes, I tried him on the buckle first, and yes, it was like hitching up a sled dog. Wear your helmet and always be mindful of how to bail and always be READY to bail! When we first started, I just took out the bike, let him sniff it, let him see me with it, then I walked him with the bike to the front door, locked it, then started on my way. I gave him time to see that I didn't really "care" about the bike and that it was just another silly human thing, but I didn't give him much time to think about whether to be worried or not. Know your dog and know how s/he reacts to new and novel situations.
Before starting, note the condition of your dog (fat, thin, muscled, little muscle) and especially its paws (pads, nails). If your dog is young enough where jogs are an issue, don't bike yet or only do a very very short trip (down the block and back or just a couple minute) solely for training purposes and fun. Don't want to hurt those joints! If your dog's pads are really soft, bike on a softer surface or walk on pavement more often before starting so the pads have a chance to toughen. If the nails are long, biking on a rough surface will wear down the nails, but if they're way too long they could interfere with gait and could lead to pain. Judge your dog's stamina to judge how far to go. It's good to get the dog nice and exhausted, but not to the point of keeling over or even harm. Make sure your dog is well hydrated before and after the exercise, but refrain from feeding until well after the exercise (or well before, I prefer feeding after). Check pads frequently during biking, especially during the first several runs. Make sure to get between the toes and note if your dog acts anxious about a paw! Watch the dog closely and let him tell you how he feels about the speed. I'll set it at first to make sure Renji doesn't overdo himself, but once I know he's got all his spazzies out, I'll look to him. If he's enjoying himself and wanting to go, I'll keep the speed up within reason. If he starts to fall behind even a teeny bit, I'll decrease speed until he's satisfied. Watch the dog's tongue and also keep an eye on the gums (watch for over-exhaustion and heat exhaustion). On warm days, especially here in Florida, be aware that heat and humidity gets to them a lot quicker and harder, especially if they live the Air-Conditioned life!
Things I would do differently: I would start with a Springer attachment but even before that, on walks I would teach slow down and directional commands, especially if I planned on using a front hitch so he could pull me AND the bike. I would also have found a better surface, but here the only bike trails that are currently open are on asphalt.
Renji's pads are pretty solid though, and he was doing great until the VERY end- I think he hit a little rock or something. Came to find out his right forepaw is nicked; not enough to bleed but enough to probably be annoying. Even if I did got a springer, I think I would still have him on the prong for control purposes. One thing I worry with the bike attachments is the safety breakaway- it's fantastic if you take a spill or happen to put a tree between dog and bike, but if your dog's strong enough to bust it to go after a cat, the dog could be gone before you know it. Even the best training can go unheeded (dogs are dogs), and all it takes is a split-second, so I'd prefer to have a backup of some sort. I was also pondering about an e-collar being a good backup as it eliminates the leash that could still pull you over, but we're not there yet.
Oh, be a VERY proficient biker as well, enough that the usual biking operations is second nature, that way you can focus more on the dog than on biking (be safe, of course). And HAVE FUN! If you're worried about a fall, bike on grass for a little while so a spill will be less painful. Watch for burrs and other spikey goodies (we have lots of those here).