Do most of your training in a pool with a pace clock. Today's top ocean racers do the majority of their training in a 25-yard or 50-meter pool using interval training with a pace clock.
Don't just lap swim by yourself, or you'll stay at the same (or slower) pace month after month. If possible, train with a group in a structured workout with a coach. If that's not available, find a training buddy.
Do mix it up. Alternate longer, paced swims with shorter distances such as 100s or 200s with little rest. You will cover the same total distance, but using different approaches will keep workouts interesting.
Don't avoid (or loaf) kicking sets in your workout, using the excuse that you'll be wearing a wetsuit in competition. Developing a good kick is more about technique and lessening drag than it is about generating forward propulsion from your legs. Practicing your kick will help improve your overall streamlining, body balance and rotation.
Do "cross train" in the water by attempting other strokes besides freestyle. This not only breaks up the monotony of long freestyle sets, it challenges you to coordinate different motions in the water. Ultimately, it will help you develop that elusive "feel" for the water that all great swimmers have.
Don't attempt to swim in open water until you can comfortably swim a strong half-mile in the pool. Once you have developed sufficient endurance in the pool, get instruction on swimming in open water by taking a clinic or swimming with more experienced buddies who are willing to teach you the ropes.
Do practice "in and outs" during your ocean workouts. Races can be decided on how you ride the waves. Dolphining off the bottom is the fastest method of getting out through the surf until the water is about chest high. Body surfing is the fastest way in. Go to the beach and practice.
Don't swim alone. When training in open water, always swim with at least one buddy, preferably one more advanced than you.
Do see the "Big Picture." Remember your long-term and short-term goals, and recognize what you're doing and how that relates to the overall goal. Be patient with yourself and enjoy the journey.