Ironfish653

Make sure the hitch is as low as possible on your bike. All the pivots should move freely, but shouldn't have any slop in them. We have an Instep Pathfinder that required some 'massaging' of the pivots to eliminate a side-to-side 'flop'

For your bike, make sure your rear tire is at sufficient pressure. It's carrying a lot more weight, so you'll need to increase the pressure over where you usually ride.
I'd also put a wider handlebar on if you can. My bike was fitted with a generic alloy 630mm 'MTB riser' bar, and it really increased the leverage on the front wheel, so you can more easily counter any unwanted changes in direction.

Riding tips: For the 'captain,' pick a gear that's a step or two lower than you usually use, and be prepared to turn the pedals a little bit faster for a little bit longer than you usually do. Try to shift gears before you need to, the extra weight will just make a late shift worse.
Actually, try to keep pedaling, even if it's just loafing along. These kinds of rigs tend to handle better 'under power' than coasting.

For the 'stoker' pedaling in sync isn't required, but they'll often fall in to cadence with you just out of reflex. You do want to tell them that if you stop pedaling, they need to stop pedaling. Nothing like having your 'trailer' trying to overtake you under power, as you try to brake for a corner or stop.
I usually will call out 'slowing,' 'stopping,' or if there's a big bump ahead so she doesn't get surprised.