For many people, moving from a single engine to a twin engined power vessel is a big step. If you are used to an outboard or inboard-outboard, it will take a mental shift when learning twin engines with shaft drive.

The first difference you will notice is that operating astern propulsion is not as effective as on vessels with legs. The rudder is not effective when going astern until you have the boat moving and water flowing across the rudder.

Rule 1 for beginners:
Neutral is your best friend - especially as the size and weight of the vessel increases it is important to keep the speed of the vessel at the minimum required to retain control. Speed is your enemy and when you go into gear only stay in gear 1 - 2 seconds. This will prevent the vessel from gathering speed which gives you less time to react and think. Usually the objective is to coast the vessel to its berth. When you have 65,000 lbs. under you, that is a lot of momentum.

Rule 2
To start we will have our engines at idle and the rudders centered. Mostly we will use only the gear levers to steer the boat. There are a number of memory aids to assist you in operating the controls.
1. Pretend the two gear levers are the handlebars of a bicycle. If you want to turn to port, move the gear levers the same as you would with a bike. In this case Starboard engine forward and Port engine astern.

2. Stand at the helm and grasp the gear levers, one in each hand. If you lock your elbows and simply rotate your upper body so you are facing the direction you want the boat to move, you automatically move the correct lever in the correct direction.

3. Imagine parentheses(curved brackets) alongside the gear levers. For example, if we use o to represent the gear levers and the parentheses would indicate the direction the boat would move.
(o o) If we move the port lever forward, the boat would move forward and the bow would turn to starboard.

Most of the time when docking or undocking you would have your rudders centered and the engines at idle. You handle the boat by moving only the gear levers.
To execute a slow turn to starboard, you would move the port gear lever forward. To make the turn tighter, you would move the starboard lever astern(reverse).

For further education: Basic Power Boat