Kubik is a quadruped robot that I'm building to learn about this kind of stuff. It started out as a simple two degree of freedom per leg quadruped robot made out of meccano-like parts controlled by arduino, but evolved into a three degree of freedom quadruped with a wooden box for the body and a Raspeberry Pi for the brains.
- Adjust the leg length to the servo torque.
- Have a power source with enough amperage to drive all the servos at once.
- You have to move the center of gravity of your robot if it only has 4 legs. Or maybe have huge flat feet, but I didn't test it. So either have inverse kinematics and shift the whole body sideways, or maybe have some tail or something. No idea what people do for the 2dof legs.
- Forget about using the speed and acceleration limit features of your servo controllers, as they are all linear/exponential, and your legs will have to move in arcs, so you will have to drive them every frame with software anyways.
- When placing the battery, consider weight distribution.
- Use screws, velcro tape, and plugs as much as possible, avoid glue, duct tape and soldering wires directly into the boards. Sooner or later you will need to replace or move them around.
- Make sure all the ports of your boards are accessible without having to disassemble the whole robot. For instance, the USB port of the servo controller – even though you already set it up correctly, you are going to need to make modifications.
- Arrange for a way to power your robot from and external source instead of battery – saves a lot of hassle during those debugging hours, you don't have to keep recharging.
- Don't forget to disconnect the battery or external power when connecting to your computer. Best, have a switch that disconnects power to the servos.
- If possible, use servos that have ball bearings for the hips (the ones that attach to the body).