It depends what you mean by a basic conversation.
After a year, I think you could expect to operate as a tourist without a phrasebook.
Simple transactions like asking where something is. Shopping. Ordering a meal (although probably not reading a menu!). Buying a train ticket. Things like that.
On a conversational level you could probably describe what you have done recently and maybe a bit about your background. Your country, your work, your family.
It tends to be one sided however. You'd have problems with the native's side of a conversation. They won't have learned the same "script" as you and will probably use more sophisticated language than you can understand and speak at a much faster rate than you're used to. Conversation tends to be a bit hesitant and stilted from the learner's side. (and sometimes frustrating as you can't express yourself as you can in your first language)
But I'd say you have a reasonable foundation for basic conversation if you can ask questions. As long as you can pick up on the response and ask an intelligent follow on question, or be prepared to answer a similar question yourself. It will probably be factual and based on events.
In "basic level real world", you can use other strategies and fall back on pidgin language, a mix of English and Japanese, pointing, writing. All sorts of things. Not good in the classroom but with a friend in the real world you do whatever it takes. Ideally you want to have the skill not to have to do this.
The next stage would be introducing opinions (more than just like and dislike) and conjecture and being able to structure an argument.
What to do? Well as soon as you can, find Japanese people to talk to. Either someone with good English but very patient and has an ability to reduce their Japanese to your level; these are usually teachers of Japanese however, or someone with as poor English as your Japanese is poor; this forces you to speak Japanese and "negotiate" your way around a conversation. It is possible to find conversational partners on the Internet at places such as mixxer
http://www.language-exchanges.org/
Skype is good because it allows for written exchange as well which smoothes out pronunciation problems sometimes. You can also have speedy access to electronic dictionaries for unknown words.
Messaging can also be an easier way to practice in the beginning as the speed of response can be slower than with talking and yet a conversation can still happen.
Also rehearse for conversation by reading and writing. Learn phrases rather than just words. Be then able to slot new words into those phrases. Try sample dialogues that you find in textbooks. There is a technique called shadowing that can help you improve speed and flow of speaking.
Also as an aside I think classroom hours are a better way to describe how long something takes, rather than how many months or years. Much harder to work out though.
Conversation is a pinnacle of language interaction and is quite difficult and sophisticated when you think about it.
I read an article recently on the Daily Yomiuri site
http://www.yomiuri.co.jp/dy/features/la ... Y14004.htm
If one looks at the field of conversation analysis, one can find myriad features that adults regularly apply in L1 (first language) conversations. Among these are turn-taking units, complex sequencing, pragmatics, topic-selection and change, repair, features of face and politeness, the appropriate choice of gambits, elaboration and extrapolation, those key features of extension and development. Most of these demand higher-order cognitive and social interaction skills.
It had interesting things to say about the difference between a conversation and an "instrumental exchange". It was about teaching English as a second language at primary school level.
