there are organizations that specialize in investment clubs and investment partnerships.
http://www.ehow.com/how_3505_start-inves...
http://investmentclubhelp.com/
http://startinginvestmentclub.com/
Basically you are estasblishing a partnership where you can act as the general partner.
Most major brokerage firms have the paper work you'll need to establish a brokeage account
Draw up a partnership agreement, find investors, invest.
I'm thinking about pooling together money with friends and family to start an investment partnership with me as the manager. How would I go about doing this?