Step 1: Getting to a running state
Step 2: Push like heck
Put the car in second gear (possibly higher depending on how fast you're rolling when you engage, press in the clutch pedal, and push the car until you get as much speed going as possible. It's best to have a long stretch to go down and nothing to worry about running into, but depending on how many pushers you have and how light the car is you can get away with some fairly short runs. Just remember that the more momentum you can build up the more likely your bump start will be successful.
Step 3: Use your momentum to start the engine
Make sure to give it some gas as you engage or you'll likely stall the engine out. If it stalls anyway try again and see if you can get a couple more people to help push. Make sure you figure out what's causing your starting problem ASAP so you won't be push starting any more. As mentioned in the intro, you can also push start any motorcycle with a clutched transmission. This is very useful since motorcycle batteries carry less charge and they're usually small enough for the driver to push and engage the motor themselves. Pictured below is an old board track bike which was designed needing a push start every time because it's stripped down to save weight. Happy trails.