Traditionally, the bride and groom sit at a 'top table' with their parents, the chief bridesmaid and best man.
However, if you want to avoid any complicated family politics - if your parents are divorced and are attending with their new partners, for example - it can be easier if the bride and groom host one table of family and friends and each parent hosts their own table.
When it comes to everyone else, don't be afraid of mixing up generations. This often works well, jollying up the older generation and keeping the high-spirited younger guests in check.
Tables for six to eight people are ideal. Make sure each guest knows someone on their table and has a like-minded stranger nearby.
As a rule, couples sit on the same table, but not next to each other.