I find just going direct to the hotel for Harrahs properties and utilising SmarterVegas/Fatwallet is the best way. I've yet to find anything cheaper than this way for all of their properties.
For other hotels using the above sites will often give you deals and if you're putting plenty of play the way of Venetian you can get their poker rate which is good albeit non inclusive of the resort fee. Booking the rooms via Dave1961 here will get you a slightly more expensive day to day rate which when you factor in tax/resort fees and weekends I think it worked out slightly cheaper for the Venetian @ $180 per night, split between 2 it's for nothing really.
Demps can probably hook you up @ Wynncore now he's a semi permanent resident for anyone that's looking to go there

I find that booking hotels this early is not really all that beneficial unless you lock in a sick deal that's unlikely to be bettered and then I still like to make sure it's one which you only pay 1 night that can be cancelled. I normally start booking rooms in January and then discard the ones I won't require closer to the time I am heading out.
Flights on the other hand are a nightmare and I always try to book my flights as early as possible. The sooner you can get them booked the cheaper they are, as Simon Galloway says it's a premium leisure route so the airlines very rarely give much away and the longer you leave it.
Although it might not matter to most poker players, for the general vegas goers it's worth noting if you fly with Virgin flights are around 700 pre june 23rd and 900 from the 23rd onwards. If you're just going out for a bit of the series or whatever then it's a couple meals or something you could save by going a day early
