The more you say in the language, the more you are showing what you know.  Obviously this is helpful in a situation where your language ability is being evaluated.  It can also make casual conversations more comfortable and enjoyable:

• In a conversation with a native speaker, if you give very short answers to questions, that puts more of a burden on the native speaker to come up with additional questions and keep the conversation going.

• This feels unnatural, more like an interview than a conversation, and it can be an uncomfortable situation for both of you.

• It could also cause the native speaker to give up on the interaction, and then you would lose out on the opportunity to practice speaking.

When someone asks you a question, don’t give a one-word answer if you possibly can say more.  And don’t stop at one sentence either:

• Expand on the topic of the original question, or move onto related topics.  If someone asks you about your favorite food, you might say that you love lasagna.

• From there, maybe you say that your grandparents came from Italy, or talk about your mother’s amazing cooking, or your favorite Italian restaurant, or tell a story about a time when you tried to cook lasagna but you forgot to boil the noodles, or discuss your opinions about the slow food movement. 

Obviously how you can expand on a topic will depend on your level in the language, but even a string of very simple sentences is better than a single word: 

• Maybe you say, “I like lasagna.  My mother makes good lasagna.  She is a good cook.  My father does not cook.  He is a doctor.  He works in a big hospital…”

• In this string of short, simple sentences, you have given the person with whom you are conversing five different pieces of information that could spark follow-up comments and/or questions.

When you are talking, you may hear yourself making mistakes, searching for words, or stumbling over your sentences. That’s okay.  Just keep talking even if you make mistakes or are uncertain.  Usually the person you are speaking with is eager to let you express yourself and will ask questions for clarifications or offer a little help along the way. 

(These suggestions are based in part on Boris Shekhtman’s book How to Improve Your Foreign Language Immediately:  Foreign Language Communication Tools)