If you load also a skeleton when importing the mesh file (see the tutorial), i make a tool that assign automatically the vertex to bone, the result i think is very good, you can also apply a random animation to see if the assignments are good, otherwise is sufficient change only some vertex.
Go to "m2tw_3dstudio_scripts.chm" > "Mesh" > "Using Auto-Weighting". But obviously i don't write now assign and use skin modifier, i suppose that if you use 3dstudio you already know some basic
PS: if you add only one bone into skin modifier list, the script automatly assign all vertex of this object to bone, example, if you select the head object , you apply a skin modifier and you add only the bone_head, the result is that all vertices of head mesh was assigned to bone_head.
This can be a good beginning to see quickly the result in game.