The Silicon Valley "two-pizza" rule is often attributed to either Amazon's founder Jeff Bezos or its CTO Werner Vogels. It says that project teams should be limited to the amount of people that can be fed by two pizzas. 

Now, it's possible to take this rule too far - what size are the pizzas? How thick? What kind of cheese and toppings? If the meeting occurs just after lunch, two pizzas could probably feed tons of people. Just joking!

The spirit of the rule, though, is that the group should be small enough to be flexible and light; team members should be able to easily and freely improvise, innovate, and bounce ideas off of each other all the time. This leads to quick decision making, smaller hierarchy, faster response, more efficiency, and speed.

Most first-time entrepreneurs, according to Othman Laraki (Director of Search and Geo teams at Twitter), think that there is a particular sequence that has to be followed. 

Here’s the typical progression: come up with an idea -> find a partner -> build a prototype -> launch -> raise money -> grow from there.

However, everything in the sequence is interdependent, and completion of one or more of the list items will help accelerate the other steps. You should not wait until one step is finished before moving on to the next one - there’s no particular order that has to be followed. You can and should do them out of order. Do what you can at the current moment and set up a bunch of parallel processes that all the steps are moving.

This ensures movement with speed. Whatever you finish first will accelerate the others and increase your overall chance of success.