The major piece of advice that I have learned is that you need to measure everything, and then measure again. Make sure that you have the physical space for your equipment before you buy it.
Most equipment is mounted on stainless steel tables and then those tables are either tacked to the floor (if you have a metal floor) or braced against the sidewall, preferably against a stud. However, food trucks are a bit different than trailers. The majority of food trucks that I have seen all have custom constructed interiors.