Table manners are by no means natural (as will become obvious when you witness, horror-struck, the graphic scenes that accompany very young children's mealtimes). Eventually you will have to teach children to wield and knife and fork correctly, not slurp from a glass, and may even introduce them to the arcane mysteries of correct cutlery usage, tipping soup bowls way from you etc.
Don't get bogged down in these minutiae. Concentrate instead on the absolute essentials. And always bear in mind that if you get too uptight about manners, you will turn family mealtimes into an absolute purgatory that is dreaded by children and adults alike. Repeated lectures about nagging remarks about shortcomings do not make for a convivial atmosphere.
Absolutely Essential Table Manners
Wait until everyone has started before you do; if you are specifically invited to start immediately, it is acceptable to do so.
Always eat with your mouth closed.
Always use cutlery (fingers are for bread, fruit and barbecues)
Never reach across the table and help yourself to food; always ask for food to be passed to you (a please won't go amiss).
Eat as much as you can, then put your knife and fork together on the plate to indicate you have finished.
Ask permission to leave the table, or wait until there is a general move to do so.