Much depends on the bloodline, the temperment of the dog must be laid back has the pup come from a good working back ground? I have never trained a Lab yet, but you should start with allowing the dog to play with deer legs, get the pup used to the smell of deer as soon as you can.
Train the dog only on deer, what you must not do is allow the dog to think it can hunt anything it likes, if its for bloodspooring deer, then train it for that and nothing else.
My dog is a Bavarian; this breed is only used for tracking and bloodspooring wounded deer, I have learnt a great deal from two very good books which I can recomend to you.
Working with dogs for deer by Niels Sondergaard. Available from the BDS
The specialist Gundog by Guy Wallace also from the BDS
My Bavarian is now 20 months old, and is still learning, they really dont come into their own until they are 3 years old, however he has found 3 deer up till now. His big test will come in about 3 weeks time when he will be in Scotland for 2 weeks on Sika and possibly some Red hinds on my 8000 acre lease. This should light his fire hopefully, cant wait to see how he performs.
Good luck with the training, let me know how you get on.