For standard service I usually tip 20%. If service is outstanding, 25%-30% is appropriate. If a sommelier does the wine service, than one can tip only 10% on wine (most sommeliers are paid by the restaurant based on overall wine sales), if one's waiter does one's wine service, then one should tip equally on wine and food.
My personal preference is to simplify my tipping by calculating the whole number about 20% on everything including wine.
/carmi