A Lattice always begins as a 2 x 2 x 2 grid of vertices (which looks like a simple cube). You can scale it up and down in Object Mode and change its resolution through the Lattice Panel in the Editing Context Buttons U, V, W. After this initial step you can deform the Lattice in Edit Mode. If there is a Child Object, the deformation is continually displayed and modified.

Now we are going to see a very simple case in which having a lattice will simplify and speed up our modelling job. I have modelled a very simple fork using a plane subdivided couple of times. It looks really ugly but it's all I need. Of course it is completely flat from a Side View. Wow, it is really ugly (An ugly fork.). The only important detail is that it has been subdivided enough to ensure a nice deformation in the Lattice step. You cannot bend a two vertices segment!

An ugly fork.

In Top View, now add a Lattice. Before changing its resolution, scale it up so it completely envelopes the fork's width (A 2x2x2 Lattice.). This is very important. Since I want to keep the lattice vertices count low (it doesn't make sense it has the same number of vertices than the mesh, right?) I need to keep resolution low but still set the lattice to convenient size.

A 2x2x2 Lattice.

Adjust the Lattice resolution to complete the fork's length (Use a suitable resolution, but don't exaggerate.).

Use a suitable resolution, but don't exaggerate.

Now, we are ready for the fun part. Go to the Modifier panel and add a Lattice modifier and enter the name of the Lattice object, created above, in the "OB:" field. Enter Edit Mode for the lattice and start selecting and scaling vertices (Deforming the lattice is a pleasure!). You might want to scale in X or Y axis separately to have more control over the lattice depth (to avoid making the fork thicker or thinner).

Deforming the lattice is a pleasure!

Note that if you move the fork up ad down inside the lattice, the deformation will apply in different parts of the mesh. Once you're done in Front View, switch to Side View. Select and move different vertices sections to give the fork the suitable bends (Bending things.).

Bending things.
Lattice Modifier

You can get rid of the lattice now if you're not adding any other child object. But before doing it, you might want to keep your deformations! You can do this by clicking the "Apply" button on the Lattice Modifier; see (Lattice Modifier).

 Mad vertices On rare occasions, for fairly complex meshes, application of the "Apply" button will look like it has damaged your mesh completely. This is false. Just step in and out of EditMode (⇆ Tab) and the mesh will be back nicely deformed as you expected.

A nice fork.