The left pedal tightens the wrong way, and forcing it ruins the crank arm for good.

The left pedal is reverse-threaded, and getting it wrong is permanent

The pedals are marked R and L and they are not interchangeable. The right pedal threads into the right crank arm clockwise, as you would expect. The left pedal has left-hand threads and tightens counterclockwise. If you turn the left pedal the usual way it will bite, feel like it is going in, and cut a new thread across the existing one in the crank arm. That damage is permanent, and on an inexpensive bike the crank is not realistically worth replacing. Start every pedal by hand, several turns, with no tool at all. If it does not spin in freely with light finger pressure, it is wrong. A little grease on the threads also stops them seizing in place years later.

The brakes are not adjusted, and Huffy warns about it

Their manual carries an explicit warning that you must adjust the front brakes before riding the bicycle. Out of the box the pads are rarely positioned correctly against the rim, and the cable tension is not set. Squeeze each lever and check that the pads meet the rim squarely, both sides, without touching the tire and without the lever pulling all the way back to the handlebar. Then test both brakes at walking pace before anybody rides properly. On a child’s bike this is the single most important thing you will do.

On coaster brake bikes, one bolt is the entire braking system

Bikes that stop by pedaling backward have a brake arm that must be securely fastened to the fork mount. Huffy states that if that bolt is removed, or the arm is loose, the brake will not work, and they ask you to check it every time the bike is ridden. It is a small fastener that does not look important, and on a bike with no hand levers it is the only thing stopping the rider. Check it on assembly and check it again periodically, especially on a bike that gets dropped and thrown around.

Torque matters in both directions

Huffy publishes a torque table and refer to it throughout their manuals, and their own framing is the useful one: parts that are not tight enough can come loose or work poorly, and parts that are over-tightened can be damaged. That applies particularly to the stem faceplate, the seat clamp and the axle nuts. Tighten faceplate bolts evenly, a little at a time in rotation, rather than fully tightening one and then the next, so the bar is clamped squarely.

Check the steering, the wheel and the derailleur before it leaves the driveway

Three quick checks catch most of what goes wrong. The handlebar and fork should turn left to right smoothly with no notchiness or binding. The front wheel should spin freely without wobble and stay firm when you push it sideways, which tells you the axle is properly secured. And on a multi-speed bike, if the rear derailleur looks bent inward toward the spokes, do not ride it until that is corrected, because a derailleur that goes into the wheel takes the chain and the rider with it.

Do not cut deep into the carton, and mind the seatpost line

Two small ones that cause real annoyance. Brake cables and inner tubes sit tight against the inside of the box, so a blade run deep along a seam can slice one before you have started. Cut shallow. And the seatpost has a minimum insertion line stamped on it, which is a structural limit rather than a guide: raising the saddle past it for a growing child leaves the post inadequately supported in the frame. If the bike is genuinely too small, it is too small.

Missing or damaged parts, and the manual for your actual model

Huffy publishes separate manuals for kids handbrake bikes, kids coaster brake bikes, BMX models with a gyro or detangler, cruisers, comfort bikes and multi-speed bikes, and the differences matter. Download the one for your model rather than working from a generic guide. Their manuals also open with a request to contact them before returning the bike to the store, which is worth knowing on Christmas Eve when one bag of hardware is missing and the alternative is a wasted trip.