SAT Prep - Writing

I versus Me may seem complicated at first, but the rule is very simple:

• "I" is used if I am the subject of the sentence (I am doing something.) 
  
  • I hit the ball (I am doing something- hitting the ball)
  • I went to the store (I am doing something- going to the store)
  • Kelly and I like pizza (I am doing something- liking pizza)
• "Me" is used if I am the object of the sentence (something is happening/being done to me)
  • The teacher yelled at me (Something is happening to me- I am getting yelled at)
  • The ball hit me (Something is happening to me- I am getting hit by the ball)
  • My new friend likes me (Something is happening to me- I am being liked)

So, when you look at a sentence- simply ask yourself- am "I" doing something?  Am I feeling a feeling, or doing an action?  If so, then use "I".  However, if I am not doing anything- if I'm just standing there and someone is doing something to me, then use "me"

Lets look at the following example of an Improving Sentences question that contains an "I" versus "Me" error:

Kelsey and me (A) like pizza, but (B) we prefer tacos because (C) tacos tend to be much tastier. 

Choice A is an error because I am the subject of this sentence.  "I" am doing something (liking pizza).  Nothing is being done to "me". 
Choice B is not an error, the proper transition is used here since we are contrasting two things (our taste for pizza versus our taste for tacos)
Choice C is not an error, the proper transition is used here since the subsequent phrase (tacos are tastier) explains the preceding phrase (we prefer tacos)
Choice D is not an error.  The comparative form (tastier) is properly used since two things are being compared- tacos and pizza.