To get clients, the approach depends on the country where you work, marketing can need to respect some rules / laws specific to the country.
You say that some words can be interpreted differently by the clients, that's why it's important to sign specifications where you describe all what will be developed with concrete examples. You also need to speak with the client before signing the specifications and inform him / her about all what is important.
Effectively there can be situations where you have to work more, sometimes to work less. More you are precise in the specifications, less there will be possible interpretation.