What do you do when you are unsure about how to achieve the goals of the team?How will you motivate team members to contribute ?

i usually motivated with appreciation with rewards and recognition, discussing about there contribution towards achieving the targets, Moving friendly with, taking for a team outings. 

If you are unsure how to achieve the goal, try working backwards rather than forwards.   In other words, if we have to deliver X at time T in the future, what stage do we have to be one day before T?  One week before?  One month before?   Don't try to do this on your own - involve the senior members of the team.