Welcome!

1) Roads occur in rings or loops. Train the inner rings if you have a large or high level train as they yield greater reward.

2) The desert is a great place to train as "hordes" (vast amounts of enemies at once) appear with relative frequency. It can often be a good idea to stay in the desert if you find a large one, assuming you can conduct your train to stay.

3) A spread out train is a poor train. Keep the train bunched together and have no one running off ahead or you're losing potential experience. If you find you can't keep your train bunched as it is too large, it might be a better idea to start a new train or move your train to an inner ring.

More to come.