Make sure you read everything on the quote, including the fine print, so you understand clearly what is and is not included. Some services and costs you might want to confirm the inclusion or exclusion of are:
Get everything in writing; if an issue comes up later and it's not in writing you'll have a very hard time arguing your case.
Once you have received all the quotes from the in-home surveys, you should compare them to make sure they are quoting for the same services. If one does not include Terminal Handling Charges, for instance, the quote will be significantly lower than the others.
If you can, break the estimates down by cost per cubic feet (or cubic meter, or pound, or kilogram, etc).
It's important to note that price isn't everything. Use the reviews on this site to determine which companies are reputable. Spending a bit more on a reputable company will be worth it in the end.