How should I name my Tables when creating a new database?

Singular: Client or Plural: Clients?

Up to you. Just be consistent though.

Personally I prefer singular based on what each *row" stores: Order, Product, User, Item, etc.

This matches my modelling (via Object Role Modelling) where I use singular entities/types.

Edit:

One reason is that plural fails when you have link tables:
Orders, Products would give OrderProducts or OrdersProducts. Neither sounds correct

Or history tables (of course you can use schemas for this):
Orders -> OrdersHistory or (no!) OrdersHistories? Wouldn't Order-> OrderHistory be better?
