Like all projects you should always go in with a solid plan. Before picking out my table design I did a fair amount of research on touch screen monitors, touch screen add-ons for regular monitors and multi touch surfaces in general. I chose to use the Acer T231H for a few reasons. Its reviews were fairly good, it was a size I felt would work well and its corners are very square, making it easier to fit into the table.
I decided that I wanted to mount a mini PC under the table. I chose the Asus Eee Box EB1021. It is small, it has built in wifi, it comes with USB 3.0 and has HDMI output. It also comes with a VESA mounting bracket which made my life a LOT easier when it came to final placement.
Find the plans for your table. There are plenty of free and paid plans online. I chose this set of plans: http://ana-white.com/2012/05/plans/itable
If you decide you want a bigger or smaller table adjust your plans accordingly. I chose to make my table 3’ x 4’ foot with 18” high legs.
Draw out your table using the measurements you have decided on. Make sure you clearly mark where you want your monitor to sit and where you want to mount the PC. It is a good idea to wait until you actually have the electronics in hand so you can get accurate measurements. I modified the size of my table just slightly to accommodate everything I wanted to do with it. The more time and thought you put into this part the better your finished product will be.