When possible, design from BOTTOM TO TOP and the check it TOP TO BOTTOM for consistency. Or you can do that process in reverse. Start at the top and work your way down and then back up. This is the BTT-TTB or the TTB-BTT approach to 3d design. There are also times where it's best to start in the middle. That doesn't fit those acronyms well, but keep that in mind too.  Maybe you could think of that as starting with the "hyphen". 

But design for what you might ask? and how?   Great questions too. 

There is an acronym used to design robots and automation systems that has application in far simpler design scenarios too. That acronym is "LOSTPED". It stands for Loads, Orientation, Speed, Travel, Precision, Environment, and Duty cycle. 

Although this is not a robotics application (yet), the LOSTPED concepts are still relevant or can be modified to be relevant -- and answering these questions in writing is the  proper place to start for any type of mechanical design: 

1. Load - how heavy are the objects you want or need to suspend? How heavy is your stand itself? What "torque" will be put on different components based on the loads (aka what moment loads will exist)?  Are there any loads that will exist as a result of motion or acceleration?

2. Orientation -  What is the general orientation of the stand and the components mounted  (ie bottom , side or top mount with sensitive parts of loads facing down, up, sideways, other or not relevant, etc) How tall or long are the components you feel you want or need and how are the oriented with regards to each other.  is everything operating in three distinct plans or are there multi-planar angles involved?

3. Speed - how fast do you need to be able to setup the stand and/or mount the loads and/or adjust the loads?  How fast do the loads need to be able to move if they can move?

4. Travel - How far does the post need to telescope (if at all)?  How far does the monitor need to tilt or spin (if at all)? How much leveling motion may be needed? 

5. Precision - how accurate and repeatable does the positioning of the loads have to be ?  Accuracy is about how close to a target they need to get and repeatability is how close they can return to a prior position (that may or may not be accurate). 

6. Environment - what environment is this operating in? Indoor or outdoor? Any moisture, temperature, UV, chemical or dust issues that might affect materials or performance?

7. Duty Cycle - How often and how far might the loads get moved? What directions to do they move? are this linear or circular motions?  are there accelerations and decelerations involved? How often might the stand get broken down or setup? How many times might a given screw or nob get turned ? etc