Once you've got them nailed, since they are more akin to learning an alphabet, then you can really start on the kanji. You'll need them to look up the readings of the kanji in most dictionaries anyway.
The ??? are not an alphabet.
I never said they were, i said they are 'more akin to learning an alphabet', ie Once I know hiragana, I can 'spell' out any Japanese word using it without needing to know the kanji.
For those that are curious a very rough breakdown of what each type of kana is used for:
Kanji - Meaning of the word
Hiragana - Grammar
Katakana - Foreign words
These aren't entirely strict though. For example, there are some words which contain no kanji and are written entirely in hiragana, and katakana is sometimes used for other reasons, such as onomatopoeia (sound words).
Before I comment further, I was learning at uni, so I had teachers/classmates/resourses/etc.. at my disposal so I can't give too much help on exactly what works well as my textbooks relied on the fact that I had a native japanese speaker to clarify some of the finer points (My textbooks were Situational Functional Japanese Vol 1-3 Drills and Notes, so 6 textbooks all up there, and some kanji book which relied heavily on being in use in a full blown course, sorry can't remember the name of it right now, but was something like Basic/Intermediate Kanji Drills....)
To extend butaro's comments, combine multiple things. Pimsleur is great for learning conversational Japanese, but doesn't teach much in the way of grammar and obviously doesn't teach any writing what-so-ever. Rosetta Stone, as people have mentioned here, appears to be great for learning words, perhaps someone with more exposure could verify this. Remembering the Kana/Kanji are a great series which definitely should be looked into.
Once you have a grounding, find something interesting (anime/manga/video games/movies/tv/whatever) and work with that. Don't pit yourself against something too difficult to begin with though. Choosing a lengthy JRPG probably isn't the best way to get started as you will be looking up Kanji on many words to begin with.
Note: You'll need to learn radicals for looking up Kanji, but don't get ahead of yourself.
Anyway, I could ramble on. I haven't been actively learning japanese for a while now so I'm a bit rusty, but hopefully you'll get something from this.
Edit: Japanese for Busy People - My university uses these for their 'Japanese for Business' courses, which are a cut down versions of the full blown Japanese course.