How can I get into the city?

First of all, have you delivered the letter to the farmer?

When you talk to him, he'll tell you something important about the guards.

They like sandwiches!

Perhaps you can make a sandwich for them.  You have a sandwich spell in your
spell book.

There are tricks to getting all of the ingredients to the potion -- those
are covered in other hints in this section.  If you don't know how to find 
any of the items mentioned below, look for other questions that might help.

The lettuce can be found in the garden next to the farmer's house.

The ground wheat can be made from grain from the meadow.

Use it on the water wheel to grind the whole stalks.

Make cheese in the basement of the farmer's house.

And the farmer has a recipe for mustard.

You first need to grind a radish from the garden.  If you have the lettuce
and wheat, then you know how to get ground radish.

Then add the vinegar (which is sitting near the farmer) as the farmer told
you to -- click it on the bowl with the ground radish.

Mustard will appear in the bowl, and you can add it to the potion.