Round Trip Search — you can add htl/car at all stages of the process (after selecting flights, after putting booking on hold, or after purchasing).  One hotel and one car maximum.

    Multi-City Search — you cannot add htl/car to held or purchased bookings.  You must select Hotel and/or Car checkbox at the beginning of the search.  Multiple hotels/cars in each city are allowed.

    Hotel Rates — Before booking a hotel, always look at the “Room/Rate details”.  There are a few rates that are advance purchase/nonrefundable.  And some rates have a penalty for cancelling within 24 hours of the check-in date, or 48 hours, etc.