How best can you motivate your team and ensure that they stay motivated throughout the entire project phase?

1. Learning & development opportunities.

2. Recognize and share ideas.

3. Supportive to team members.

First to feel around you that one goal and success depends on everyone.

Second, that everyone feels the importance of the role of each person to the success of this project without charge anyone dereliction

Third, there must be a stimulus between the team.

Fourth: to be a direct manager is the commander-friendly and clear vision and one goal is required to achieve and everyone must feel the value of this work.

Fifth, there must be a stimulus for the employee of the material terms or moral

Sixth: you must build trust between the team members

proving healthy friendly environment and stay in touch with them continuously so that they are all the time involved

First thing is first, don't make them feel that they are working for you, try as much as you can to make them feel that you are taking the lead but you are all driving one boat. If you feel that there's a routine in daily work try doing something different, probably as small as leaving a candy on the desk of each one of them to bright up the day. 

Hope that helped

Just want to add , being just to all the team members is also important. Should be unbiased to all team members( irrespective of the un official reach that some of the team members may have). 

We live in an imperfect corporate world where some people will try to leverage their connections mostly implied rather than express to gain more facilitates and get ahead of others. If the supervisor/manager can have a level playing field for all then half the work is done.

Otherwise if he is under the influence of such unseen but powerful forces and works just to save himself he would loose all respect. 

Agree  with all experts. Friendly environment , Team work ,Create  Interest  and clear goals.

Make every  team member feel as a partner.

All team members to have equal rights when it comes to sharing ideas

All team members know that success of the project depends on all of them equally

Make the project as fun as possible for every team member

Acknowledge their contributions and their achievements

The most important thing is the realization of ownership, the realization that its their project and they are partners in success. Make them contribute freely without steeling their spotlight, this will give them sense of achievement. Recognize them on success and encourage and support them on setbacks. Lead the effort instead of managing it. There is no better motivator then the sense of achievement and being part of something important.