There are three main ways to get food in Agricola.
1. Bake Bread/Sow Fields - This is the strategy I've found the most effective.
In stage one you should plow, take grain and sow for at least one field. If you can sow two that would be a big bonus (remember you can save a turn if you sow both grains in the same action).
Assuming you only plowed one field in stage one, in stage two you now want to plow another field, and sow it with the harvested grain. You'll now be producing at least two grain per stage.
Grab either the stone, or the clay oven. The stone oven is probably better, but it doesn't really matter, and it's more dependent on what resources you have/can get. Remember you can bake bread when you first buy the oven.
From now on, when ever you sow one of your empty fields, you can also bake bread which will probably be enough to feed for your family for that stage.
2. Eat animals
Grab the fireplace or the cooking hearth. Build pastures, and grab the animals before the other players do, (though of course, if you can let them build up before the other players grab them, do so).
Remember you can cook the animals even if you don't have space in your pastures, so long as you have a fireplace/cooking hearth.
This strategy I've notice tends to be favoured by new players, but I don't think it's particularly good. The animals don't grow as quickly as grain, and they are only produced build up on one action space per animal. In games with more players this might be a better action when you can take a boar/cow from supply.
3. Collect food from fishing/travelling player/store house. This strategy shouldn't be underestimated!
In the family friendly version the 'starting player' action has storehouse (+1 food/turn), and traveling player at more players (+1 food turn). If these are at 4+ food, that's just as good as baking bread, without having to have taken all the plowing/sowing/build improvement actions in between.
For example if you take the fishing at the end of stage one for four food, that tides you over with enough food for harvest two. During stage two while everyone else is running around buying cooking hearths/ovens etc, and you can grab the wood or whatever.
Bonus: Taking the joinery/pottery/basketmakers workshop can be a helpful bonus to your food, though not a strategy in itself. At two food per harvest, if you have a big stash of one of those resources lying around.