I had training on driving a forklift about 10 years ago. The top concerns (10 years ago during the training) where:
1. The forklift is rear steering, this changes the physics of the device especially when a load is on the forks. There was an emphasis that the fork lift is NOT a car and drives differently.
2. Most loads on the fork lift are held close to the carriage, but if your load is 'long' then the entire balance of the fork lift is off. There was a chart on the fork lift that gave the max weight and position of the load. Also, the higher the load is off the ground the more the fork lift will want to tip.
3. The fork lift is typically low to the ground without shocks or other cushion. This means that when the fork lift is moving and hits a bump, the whole fork lift hits the bump. Loads will fall off if bouncing.
4. Speed is dangerous. The fork lift is extremely heavy and does not 'stop' or react quickly. While a car has been getting lighter and lighter over the years, fork lifts need the additional weight to prevent tipping. This extra weight makes the fork lift slower to react. See #1, the fork lift is NOT a car.
These are the things I remember. The training was on sit down fork lifts that were used at the plant I was at. We did not have any of the stand up types you see at home depot, Lowes, or Costco so these things may not apply to those types.