Definitely learn sumimasen for "Excuse me"/"I'm sorry." It's an incredibly useful phrase!
Why are you learning Japanese? What are your goals?
Do you like Rosetta Stone? I've never used them before, but I've been studying Japanese for about 3 years now. I find the most effective way for me is one-on-one tutors, like here at Italki!
おはようございます (ohayōgozaimasu formal) good morning
おはよう (ohayou/ohayō casual) good morning
こんにちは (konnichiwa) Hello or good afternoon
こんばんは (konbanwa) good evening
おやすみなさい (oyasuminasai/formal) good night
おやすみ (oyasumi/casual) good night
はじめまして (hajimemashite) how do you/nice to meet you
お名前 (なまえ)は何(なん)ですか。((o)namae wa nan desu ka) what is your name?
お元気 (げんき)ですか。((o)genki desu ka) how are you
調子 (ちょうし)はどう?(chou/chōshi wa dou/dō?) how are you
さようなら (sayou/yōnara) good bye (there other ways to say this when talking casually with friends. This one mean good bye for a long time)
すみません/すいません (sumimasen/suimasen) Excuse me
ごめんなさい/ごめん (gomennasai formal/gomen casual) I'm sorry
はい/うん (hai formal-casual/un casual) yes
いいえ/ううん (iie formal-casual/uun casual) no
よろしくお願 (ねが)いします (yoroshiku onegaishimasu)
いただきます (itadakimasu) Thank you for the meal (before eating)
ごちそうさま(でした) (gochisou/sōsama (deshita))
ただいま(tadaima) I'm Home
お帰 (かえ)り(なさい) (okaeri(nasai)) welcome home
いってきます (ittemasu) I'll go and come back.
いってらっしゃい (itterasshai) please go and come back
ありがとうございます/ありがとう (arigatōgozaimasu formal/arigatou-arigatō casual) Thank you (there are many other ways to say this)
どういたしまして (dou/dōitashimasite) you're welcome
はじめまして hajimemashite Nice to meet you (Used when meeting someone for the first time)
よろしくおねがいします yoroshiku onegaishimasu Please to meet you, (usually said when introducing yourself also)
If you need help with anything else please let me know. I am still a beginner also but maybe we can help each other!
こんにちは konnichiwa Hello (Usually used from 10am until sun goes down)
おはよう ございます ohayou gozaimasu Good Morning (Usually used until 10am)
こんばんは konbanwa Good evening (Usually used after sun goes down)
おやすみなさい oyasuminasai Goodnight (Usually said when going to bed)
げんき です か genki desu ka How are you?
げんき genki Good, Fine