Roald Dahl's short story "Lamb to the Slaughter" contains numerous poetic, or rhetorical, devices. Prior to providing the examples of specific devices, allow the devices in question to be defined. 

Simile--A comparison between two typically dissimilar things (using "like" or "as"). For example, the following is a simile: My life is like a highway. In this example, the speaker's life is compared to a highway (meaning it changes direction, moves forward, and has its ups and downs--like a road). Here is an example of a simile found in the text: "She loved to luxuriate in the presence of this man, and to feel - almost as a sunbather feels the sun." Here, the narrator defines that the closeness of Mary's husband feels like the warmth of the sun.

Alliteration is typically reserved for poetry (being defined as the repetition of a consonant sound within a line of poetry). That said, one can identify alliterative lines within Dahl's text.  In the opening line,"The room was warm and clean, the curtains drawn" alliteration exists. Both the repeating "w" and "c" sound illustrate alliteration. 

Personification is the giving of human characteristics to non-human and non-living things. For example, the sun smiled is an example of personification. The sun, a non-human object, cannot smile. This text does not contain any examples of personification. 

Absolutley! Similies, alliteration, and personification are all literary devices that are used in writing. 

Similies are comparisons using the words "like" or "as". For example, if someone said "the stars were shining like diamonds in the sky," he/she is using a similie because they are comparing stars to diamonds using the word "like".

Here are some more examples of similies:

After days without food, I was as hungry as a bear.

The star athlete was as fast as lightning.

The hurricane winds sounded like a jet engine.

Alliteration is when you use several words beginning with the same letter/sound in a row. Have you heard of "tongue twisters"? These are often examples of alliteration. For example, "Sally sells seashells by the seashore."

Here are some more examples of alliteration:

George gave gallons of gas to Gertrude.

Peter Piper picked a peck of pickled peppers.

Arthur Ashe was an amazing athlete.

Bugs Bunny

As you can see, not everyword has to start with the same sound. Also, it can be as simple as two names that start with the same letter - such as "Bugs Bunny" or "Daffy Duck".

Personification is when you give human qualities to something that isn't human. For example, when someone says "the thunder screamed," they are using personification because screaming is a characteristic of humans, and thunder is not human -- or even alive!

Here are some more examples of personification:

The droplet of water danced at the end of the icicle as the temperature began to arise and melt away the ice.

Time raced away as Billy began his big final exam.

The dark gray car seemed to jump out in front of me just as I turned my attention back to the road.