Make sure you are using the IFC import tool available for free download from the Graphisoft website.
http://www.graphisoft.com/support/archicad/downloads/interoperability/
It really does improve the quality of the import.
Also, install Solibri viewer (its java & runs in your browser so you can install it without admin priveledges) and use it to view the raw IFC model so you can see what is missing.
Accept that hundreds of error messages is normal when importing IFC files. I always save the error file and review it, because I'm a sad pathetic looser with nothing better to do.
Most of the errors are things like overlapping walls that dont make much difference to what you are doing.
Sometims things that should cut other geometry dont form the cut, so look out for that. Door hi-lights is a common one, they end up embedded in the wall.
Ceilings wont show the tile grid. I always ask for dwg files as well & link them in to define the tile set out.
hth
