Find bands to play at the concert. Often, a rock concert will center around one headlining act that is on tour and one or two smaller opening bands that are either touring or local. Ask friends if they know anyone who wants to play a show, and ask the headlining band if it has ideas for opening acts. The total number of bands on one bill is typically either two or three.
Find a venue to host the show. This could be anything with a big enough space for a band to set up and an audience to dance. When asking venues if they'd be able to host a rock concert, be sure to note the dates and hours that the venue is available, the kind of music it would allow, if it is an all-ages venue, and if alcohol is allowed. You can try calling bars, community centers, friends with large basements and any other space you think likely, private or public.
Set the date and hours of the rock concert. This means confirming a date with both the bands and the venue, and finding out when the show should start by counting back from that time that it must end. For example, if the show must end at midnight, and there are two bands, the headliner should play from 10:45 to midnight, and the opening band should play from 9:15 to 10:15. The doors, therefore, should open at 8:30 p.m. This will vary according to the setup and tear-down time needed by each band, and how long you want the sets to be.
Advertise. Use all available methods to promote your show, from online networks to word-of-mouth, colorful fliers and photocopied handbills. The bigger the audience turns up, the more money the bands and venue will make, the greater promotion the bands will get and the more fun everyone will have.
Find people to stand at the door. These folks will take admission money and check IDs, if needed. Set them up with stamps or markers and a secure money container. If your rock concert happens at a bar, the bar may provide door people as well as a bouncer.
Make the venue appropriate for the music. Softer rock may call for candles placed around the room. Rock with a strong rhythm should be accompanied by a nice, clear dance floor. Some rock concerts may even call for chairs around the edges of the room.
Make yourself available during the show. Try to delegate as many jobs as possible to others so that you will be able to run between representatives of the venue, the people at the door and the bands, and keep an eye on the audience as well.
Finally, be sure you are able to close the venue at the right time. This will keep you on good terms with the venue and local law enforcement (keep from getting a sound violation by shutting down on time). You may have to be pushy to get people to disperse, turning on the lights and turning off the music.
Help with cleanup--the last band will still need to tear down, and you may have to organize a crew to clean up after the audience.