Listen to local rap disc jockeys on the radio. Contact them to find out about open mic events in your area. Go to these events and talk to people about your idea to form a rap crew. Listen to different rappers and assess whether they would fit into your crew.
Use social networking websites and online forums to send out messages about your intention to form a rap crew. Ask people to send you samples of them rapping so you can hear their rap skills. Search for rap music producers to either produce beats for you or to sell you beats they previously produced.
Decide on a name for your crew. Find somewhere for your crew to rehearse. Listen to beats and music you acquired from the producers. Choose beats carefully to aid the definition of your crew's particular sound.
Find a recording studio to record your crew's song. Send your track to DJs and ask them to play it on their radio shows and at clubs. Offer to perform at rap gigs for free to get your crew's name known in the music world.