It is customary in France
to have a small drink before the meal
starts. It's not a formal custom so there is no official procedure.
L'apero usually goes something like this:
The person doing the cooking announces that the meal is nearly ready and the table needs to be set. When this is done everyone gathers around the table and each persons aperitif of choice is served. In most cases this is pastis (a mixture of an aniseed based spirit (some people think Pernod is acceptable, real conneseurs use Ricard 51) and ice cold water which turns a milky yellow) or a light wine, sirop for the kids of course. Plain crisps and other small snacks might be served including my favourite croutons - hard, almost hard biscuit like croutons heavily coated in garlic powder.
Things continue like this until the food has finished cooking, which is usually about the time you finish your drink.
As a general rule, the bigger the occasion, the bigger the aperitif. A get together with family and close friends will usually have lots of goodies bought in specially to nibble on and some more exotic drinks but most people will stick to pastis, albeit in stronger doses. Cooking may not have even started when the aperitif is called but it's always a relaxed affair. Weddings and christenings may splash out on champagne.
The idea of the aperitif is not to get drunk as some would think but to relax into the meal at a civilised pace. In the south, particularly Provence, where summer temperatures regularly reach the mid 30s, the pace of life almost demands one!