If it's to practice a specific writing style--business-related letters in this case--the easiest way would be to read various examples. Afterward, or while reading, compose new business letters about any topic.
Either 'is' or 'would be' are appropriate in this example. However, 'would be' will often be preferred in this type of sentence because it implies a possible course of action in the future, while using 'is' is more of a judgement that that way is in fact the easiest possible way.
However, especially in spoken conversation someone might choose 'is' without actually meaning the extra implication of it being the easiest possible way.
The difference could be used by a writer as a subtle way to contrast personalities, but it would be very subtle unless it was part of a larger pattern.