Focus first on the writing system. This is one place the speaker of English is in luck, as Bahasa Indonesia's writing system (huruf-huruf) is a form of the Latin alphabet. Special characters to watch out for are c, which is pronounced "tsh"; f, which is often pronounced "p"; kh, pronounced "ch" as in loch (Scottish); ny (ñ); sy (sh); v (f). Indonesian does not use any special characters, and so can be typed using a standard English keyboard.
Learn some basic phrases. Try to the word selamat first, which combines with parts of the day to make greetings. "Selamat pagi" means "good morning," and "selamat malam" means goodnight. Learn also the two words for goodbye: say "tinggal" if you are leaving, and "jalan" if the other person is leaving. "Selamat jalan" can mean "have a safe trip" or "bon voyage." To be polite, address men as "pak" and women as "bu." To find out how someone is, ask "apa kabar?" If you are well, respond, "baik" or "baik-baik"; if you are not so well, say "kurang baik."
Turn to the grammar of the language. Indonesian has a slightly more complicated system of pronouns than English. For instance, there are formal and informal words for I (saya and aku), and three words for you (anda--formal, kamu--informal, and kalian--plural). There are two words for we: kita, for when you include the person you're talking to, and kami for when you do not.
Learn the relatively simple Indonesian verbs. All forms within one tense of a verb are the same, so that you need only use a pronoun. For instance, "saya mengajar, anda mengajar, kita mengajar" (I/you/we teach). To make the past tense, add "telah" after the pronoun, and for the future, add "akan": "saya telah mengajar, saya akan mengajar" (I taught/I will teach).
Concentrate on Indonesian nouns, which have a unique feature in the plural. Anak, which means child, becomes anak-anak in the plural. This works for all nouns unless the plural nature of the noun is already implied by the context, as in beberapa turis (some tourists). There is no need to pluralize this noun because some is always plural.