place your model at the axis origin:
the centre point of the model’s ground plane is placed on the axis origin. Blue axis is pointing up
 


no erroneous outlying geometry
turn on hidden geometry and check they’re is nothing lingering around and delete it 
model naming conventions:
prefix your model names with:

• your company name or abbreviation
• the number of the model

all in lower case characters and use hyphens(-) instead of spaces eg:
tgrg–1-cube-with-corner-glazing
keeping file size to a minimum
as a general rule of thumb make sure textures are no bigger than 1024 X 1024. We recommend 512 X 512

clean your models in skethcup:

install the the ThomThom CleanUp plugin you’ll need his supplementary plugin to TT_Lib. This will literally cut your file size in half, if not more.

If your not prepared to install plugins, at least delete unused materials and “purge unused” from:

window > model Info > statistics

3ds max

simplify geometry:

use the  Attach Mesh by material to reduce model complexity.

optimise materials:

convert materials to “standard materials”. Vray materials wont work.