Hi there! Welcome to the forum....when you've got some idea of the size and the design put up some skecthes of your design and I'm sure that everyone will chip in with comments.

Make sure you read all the build logs as there's a wealth of information there and it will save you quite a lot of re-designs (ask me how I know!!) and think ahead to things like bolt positioning (can you actually get to the bolts to assemble it, disassemble it, part disassemble it for maintenance/greasing) where you're going to put your energy chain and thus cable runs, look at the rail/table design to make sure you have no dead wasted spaces (I have!!) on your table or design your table to include the dead space but so you have the working area you need...there's lots more but you'll find it beneficial to read all the various build log threads and gleen all the information from them!

Anyway welcome and good luck