How do you build a robot?

Decide what you want it to do, design it, make it, redesign it remake it... continue until it suits your needs.

It all depends on what the purpose of the robot is. Different functions have different designs. Different designs require different budgets. Is it autonomous or teleoperated? Is it stationary or movable? There are many questions you need to ask yourself when designing and building a robot.

For a start there are many different types of robot, i am actually working on a project to build a humanoid robot myself. But the first function after deciding how big, what you want it to do and so on is to create a 2d servo plan. Servos are two-way motors which move the body parts of the robot. You need to briefly draw out what positions these need to be in, label them the design the controller and label each command. A different command is need to how hard you push buttons and for each angle in an analog stick. Label each of these and for each of these, show what servos will move how much and in which order, a physical scaled version can me made from materials such as wood, but these need to be able to move in the exact way you robot can. Record the angles of each movement, in what order, how fast and so on, take in mind some programming will be involved as the robot will need to move 2 and a half steps then check if the controller is telling it to continue walking, this will need a different command as the robots foot will be in the air, if the controller shows to stop walking, a different command will be needed to use from when the controller is neutral when standing and when the foot is in the air after walking. This will be needed to put into binary (110010110101110) and into a CPU, connected to the servos.