I will only summarize.
- Japanese language not hard, you need to know only more than two thousand hieroglyphs (so called kanji) and more than fifteen thousand words, then reading and listening will be quite easy – you will can understand more then 80% of information. However, it depends on data, If you will read only science fiction and then began to read detective story – you will be surprised by big amount of new words.
- To learn how to read Japanese you must read Japanese. First it will be very slow and difficult, but with time your vocabulary will grow and reading will be simpler. Besides books, also recommend to play in Japanese games, many of them have voiceover and there you can gain many words and kanji, moreover you will know their pronunciation.
- For understanding Japanese speaking you must watch Japanese movies, anime ot news, but you must like what you do. At first it will be impossible to understand them, but do not despair, the essentials is listen foreign speech. At first you will hear only gibberish, but with time you will recognize familiar words. Do you must use dictionary when meet new word? If you wish – do it, if not – you can skip it and turn to dictionary only when meet word several times.
- In the beginning of learning don’t need to concentrate on grammar. You can gain basic grammar in any book and rest you gain while reading or listening.
- Encountered words you can write to note, but better write it in text file (at least you will be able read it later), and then transfer them in program for words learning, for example anki. If your goal is to learn as faster as possible read and understand speech, then handwriting will slow down you in learning words and kanji, the slower you increase your vocabulary, so much the worse you understand text and speech. You can do handwriting only when decide to take 漢字検定, or if you like it.
- You can search new kanji by pronunciation (if you heard it, or understand it pronunciation) or search by keys. Search by keys is contains in many e-dictinoary, for example jisho.org, you must select keys, which is part of your kanji, and you get list of kanji that contains these keys, then you select your kanji from the list.