First impressions matter, and for many their first impression of your firm will be given by the receptionist. So ensuring that they have the right personality and presentation is vital. Training on dealing with clients efficiently is needed, as is an effective system, which needs to take account of the people in the system as well.
That much is obvious. But however good your receptionist is, and however well trained, they have to be there. Therefore, their backup for any absences needs to be just as good.
Further, a good receptionist can be an effective salesperson, through knowing what the firm does (and does not do) and spotting openings during conversations with clients.
Make the most of them!