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A frequent error in English is using the wrong form of the personal pronoun:

Don't use an object pronoun when you should use a subject pronoun -- or the other way around. People often make this mistake when dealing with a compound subject made up of a noun and a pronoun:

Wrong: Amanda and me are going to the store.    
Right: Amanda and I are going to the store.

Wrong: John saw Amanda and I going to the store.
Right: John saw Amanda and me going to the store.

To avoid this problem, cover up the other noun and ask yourself if the pronoun is correct. You wouldn't say Me am going to the store. Likewise, you wouldn't say John saw I going to the store.

Comparisons following than or as always take a subject pronoun:

Wrong: Amanda is taller than him.     Wrong: My dog is as heavy as me.
Right: Amanda is taller than he.          Right: My dog is as heavy as I.

The key here: The final verb in such sentences (here, is and am) is omitted. Mentally put it back in and you'll get the pronoun right.  (Amanda is taller than he [is].   My dog is as heavy as I [am].)

A pronoun following a preposition is always in the object form:

Wrong: Anne gave the book to Ellen and I.
Right: Anne gave the book to Ellen and me.

Wrong: Michael is flying to Los Angeles with Sue and I.
Right: Michael is flying to Los Angeles with Sue and me.

Again: You wouldn't say Anne gave the book to I. Nor would you say Michael is flying to Los Angeles with I.