I was going to write a 500+ word evergreen article on my advice to Japanese beginners, but I can do one better than that.
1) Purchase Genki I, and Genki II.
2) Download Anki (it’s free).
3) Follow Adam Shapiro’s excellent walkthrough on Japanese Level Up. While you’re there, subscribe to JALUP. Once you get back here, subscribe to my blog too.
4) As Adam says, get a shared deck off of Anki for hiragana and katakana. Get the RTK Mod the JALUP store (it’s free.)
5) Build your J-E deck with Genki I and II.
6) If you’ve got $40, purchase The One Deck. It’s worth it.
7) If you’ve got some extra cash, browse the other JALUP offerings. I can’t vouch for any but The One Deck, with which I am completely satisfied. If you do get some of the other products, come back here and let me know in the comments how you liked them.
8) Work, work, work. I’ve been studying Japanese on and off for the last fifteen years, and solidly for the last four. You’ll hit roadblocks, you’ll plateau, you’ll consider giving up. Don’t. One Anki card at a time, one Japanese-language web article at a time, one audio clip at a time, you will improve.
Seriously, don’t give up. Being bilingual changes your life.