A stage plan is a very important document for the sound engineer. It shows them your line up (such as how many performers) and what equipment is being used. It shows what equipment the band has and what they expect the venue to provide. This includes microphones, placement of equipment/boom stands etc and so they can get a good overview before you even go into the venue. This gives them a great heads up, especially since many bands do the weird and the wonderful.
It also shows the engineer and the stage hand how many plug sockets the band needs and where to run cables for DI boxes and microphone leads. Where and what boom stands are needed. This is vital since there is often more than 1 act on each night so it gives the venue an idea how to change the bands over as well.
To get this overview up front makes life easier for everyone as it can often reduce any unpleasant surprises.
There are a few stage plot creators out there. Some cost and some are free. Typically the free offerings are too basic, often requiring you to print it out and write extra detail or provide it as a supporting document to the venue. stage-plan.com tries to do it all for free. If you can think of something else stage-plan.com needs, then contact us with a suggestion. If you don't ask, you don't get :)