For flight:
If you're going to Japan in May, I would wait until January to really consider buying a ticket. Unless you prefer not to wait, but I don't see the point in looking before 6 months until your expected departure date. Prices go up and down constantly.
I went to Tokyo in October 2009 and never really looked into buying my plane ticket until May-June. I enlisted the help of a travel agent who looked for flights from Ottawa, Ontario to Tokyo, Japan on a daily basis and she would report back to me.
One day, she called saying there was a 24 hours sale on a plane ticket to Narita for 950$ (+ taxes). I had to pay within 24 hours, otherwise I would lose on the sale and seats.
So if you feel comfortable getting the help from a travel agent, I definitely recommend it. They know what they are doing and if you tell them you're serious, they will be serious in their search to help you. Mind you, since you're leaving from Halifax, I don't know if you'll be able to get something as cheap as mine, since I was leaving from Ottawa which is further west of the country, so I didn't have as far as you to go.
I had a connection in Toronto, then direct to Narita. 12 hours flight practically killed me, so if you can have a stop in Vancouver I would highly recommend it.
For hotel, I highly recommend:
Tokyo hostel| Sakura Hostel Asakusa, Japan | Online booking
One of my friend used these guys to find a cheap place to stay in Tokyo and she was very satisfied. I'm not sure if they all work the same, but I've noticed a lot of them include a fridge, tv and internet in your room (if you pick a private room). There are shared rooms and all that too. Their website offers a lot of good deals year round, so just keep an eye out. I wish I'd known of this website when I was in Japan!
I've already found my hotel for my next stay in Tokyo, it's in Ikebukuro and is around 6,800Y (70$) a night for a private room.
Hope this helps!