I'm not patio11, but I've been learning for over a year now, so hopefully I can provide some decent advice. This is purely from a self learner perspective - if you're okay with taking classes, there's a completely different direction I have no experience with. (Wall of text warning)

Some general tips first:

1) Pick a method and stick with it. I bounced around from material to material, hoping to find something that just clicked and immediately made me feel like I was making progress. This was never going to happen - you need fundamentals, and it takes some time before you start to 'get it'. This is one of the toughest parts - but probably not the absolute toughest.

2) Learn the writing system. Learn the kana (Hiragana, katakana) first. This will help you in a multitude of ways, and will get you away from the awful romanizations.

3) To expand on two... Do not ignore the kanji. Yes, they seem hard and scary. There's a lot of them. A lot of them look similar. They can have multiple readings. But there's a system to them - radicals - and learning them builds vocabulary.

4) OUTPUT! Something I struggle with to this day. If you spend all of your time ingesting, and not creating, you might be able to read or listen, but then struggle when the time comes to speak or write. I'm not necessarily saying you have to learn how to write all of the kanji - though if you're wanting to live there it is very helpful. Not necessarily a deal breaker if you know the kanji and don't mind being slow at filling things out while you pull up a stroke order guide and butcher the writing - but you need to communicate with the language. Find some language exchange partners and penpals. Write back and forth. Skype. Nothing can prepare you to speak the language fluently except practice.

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Now, for some specific advice on how I would go about it based on my past experiences:

1) Pick up the Genki series of books. They're great. Two volumes, two workbooks, an answer guide. These are one of the handful of common textbooks for classes, and they have some group oriented activities in them (But there are ways to practice these elsewhere - more on that later!), but they're still one of the most comprehensive end to end guides on grammar and the fundamentals you'll need to know. Learn hiragana and katakana while working through these - after the first few chapters, the roumaji goes away.

2) While working through Genki, start using a SRS (Spaced Repetition System) to learn the kanji. There are a lot of options here. Anki + the core decks is free. It's easy to add new words from other sources - things you're wanting to read, games you're playing, etc. Wanikani is a popular one that runs on a web interface. iKnow.jp is the one I currently use, because it forces you to provide output in a handful of different ways and draw the association in more ways than just character recognition. It is not free. There are community created courses for iknow as well - including ones for genki, so you can use it to learn the vocab for a genki chapter as well.

3) Begin doing some basic output on lang-8 after a few chapters of Genki and a couple hundred kanji. You write a passage in Japanese, and a Japanese-fluent person will correct your mistakes and offer input. In return, you find a passage that someone has written in English and do the same. You can use this for your genki homework/many of the group activities.

3b) Go to the lang-8 group section and check out the skype groups. It might take a bit to find some serious language partners or pen pals, but reach out and start searching. You don't need to be fluent to muddle through some basic conversation.

4) There's some supplemental stuff out there that I've found useful - but they're not necessarily needed. Kodansha puts out a billion books on learning Japanese, and most of them have some value, but in particular, Making Sense of Japanese by Jay Rubin (Haruki Murakami's English translator) was invaluable to me in picking up several concepts that I was struggling with when learning from textbook sources. Japanese The Manga Way is also an excellent resource - it's a serious learner's resource, despite the name, and includes grammatical concepts that are covered up through the JLPT 3 test. It's very grammar oriented, so you won't really learn the vocab like you will with Genki. There's also the "Dictionary of _____ Japanese Grammar" (Beginner, Intermediate, Advanced) which are very much reference books. You would not want to try to learn from them, but they can be very valuable when you need in depth clarification on a grammar point.

5) If you're at this point, you're probably delving far enough into Japanese you can find your own way when it comes to learning, but this is probably the most frustrating point for a lot of self learners. Genki was fun, you learned a lot, but you're still probably struggling to understand native material, even things that are written for a fairly young audience. You've put a lot of time and effort into it, but you're not seeing major results. There's also not really a direct sequel to Genki. The same company produces "An Integrated Approach to Intermediate Japanese", but my opinion (Which seems to also be the prevailing one among learners) is that it just isn't as high of a quality textbook as Genki. Less fun. Less effective.

There's Tobira - which is definitely a good textbook - but there is a gap between Genki and it. It's not a huge one, and you can definitely be successful starting it right after Genki, but it's a lot harder and you're going to have to be ready to reference some outside sources and ask some questions. Hopefully you've built some friendships with native penpals by now that don't mind answering questions! After you finish Tobira, though, you should be able to begin to see a light at the end of the tunnel. You're not going to be reading native Murakami or Ōe, but young adult level fiction, news articles, etc, should mostly be in your grasp grammatically. If you've been diligent with your SRS, you should have the vocab mostly down. You're still going to need to look things up to understand the finer points or random words you haven't encountered yet. But you're now past the JLPT 3 level, and probably fairly close to 2.

From there textbooks are getting less and less useful, and it's time to start trying to immerse yourself in the language as much as you can, and using references for the things you don't understand. You can still pick some stuff up from things like "Authentic Japanese", and if you're taking the JLPT tests, the Kanzen Master series will be a good study guide. If you didn't pick up the Dictionary of [Basic/Intermediate/Advanced] Japanese Grammar series before, you probably should now.

Cliff notes: Genki + some form of SRS to start. Keep up the SRS indefinitely to learn new vocab. Start creating output as soon as you can. The sooner, the better. Tobira is a good next step from there, though a little difficult. After that you can keep going with textbooks, but should really be trying to just ingest as much native content as possible and look up anything you don't understand.