Purchase a phrase book and audio tapes (see Resources below). Either go to a brick-and-mortar store, or use an online resource (see Resources below).
Listen to the audio tapes as often as possible. The easiest way to find time to do this is while riding in the car.
Practice the phrases in the book until you can say them without great pauses between words. Once you can do this, get out your tape recorder and tapes. Record yourself saying the phrases into the tape recorder, then play it back. Were you able to get through the sentences? Did you remember what they meant when you heard them again? If so, could you possibly reply to a person who spoke that phrase to you?
Compare your accent to a native speaker's accent. Remember that there are no short vowel sounds in Japanese, so vowel sounds must be consistent in your pronunciation in order to be understood. The "a" is like the "a" in "father"; the "e" is like the "e" in "bed"; tThe "i" is pronounced like the long "e" in "mean"; the "o" is long like in "rope"; and the "u" is also long like in "soup." Also the "l" and "r" sounds are not distinguishably different in Japanese. Keep practicing and take note of your progress.
If you are able to find a native speaker of Japanese, make a point to have conversations with them in Japanese. You should buy them coffee or offer a small gift in order to be culturally appropriate. If they seem uncomfortable with the situation, do not push the issue. Even if you are unable to find a native speaker, you can get together and practice with other learners. Remember that without practice you will never truly be able to converse. Make sure to add the word "ne" at the end of sentences as often as you can. This shows you want the other person to agree and continue on in the conversation. You should do the same when someone says it to you.
Watch children's cartoons or children's shows in Japanese (not anime--most of these shows are intended for adults and the level of language will be more advanced). The levels of Japanese spoken by the characters in children's shows will be slow enough and basic enough to be understood. Repeat what the characters say and practice the intonation.
Join groups like the Japan-America Society in your area and attend local events so that you can seek out more opportunities to practice (see Resources below). Always take advantage of the chance to speak more. If you do not speak often, you will not remember and never become "pera pera" (fluent). Ganbatte kudasai (you can do it)!