Consider a Counter-Example (SAT & ACT Essay)

One of the most effective elements you can add to your essay on either the SAT or the ACT is the counter-example. When used properly (i.e. in a way that does not confuse the reader about the argument you're making), it can be the difference between an ok (8-9) score and a high one (10-12). Why? Because it shows that you're capable of considering potential weaknesses in or objections to your argument, and of addressing those objections.

Where to put the counter-example: there are a couple of places. In the simplest version, you don't even need to use a full-fledged example but simply acknowledge the opposing argument briefly in your introduction using an "while many people believe x, in fact y" structure.

So, for example, if the prompt is: "Should people take more responsibility for solving problems that affect their communities or the nation in general?" you could say something like: "While a common American myth asserts that individuals are responsible exclusively for their own actions, in reality no individual exists in isolation, and people should therefore attempt to take a more active role in improving both their individual communities and their societies at large."

The second option is to devote the last body paragraph (typically the third) to the counter-example.  Note: this is far easier to do on the ACT essay than on the SAT essay; the extra five minutes can make a big difference in terms of having a fully developed third paragraph. If you only have time for two bodies paragraphs, each of which argues a different side of the prompt, there's a good chance your essay will end up a mess.

The third option is simply to stick it in as a sentence or two at the beginning of your conclusion; in this case it's simply a shortened version of option #2.

Regardless of whether you do #2 or #3, you must use a clear transition that indicates a counter-argument (e.g. "On the other hand, people often argue that..." or "A common objection to this argument is that...") and make sure to refute it! (e.g. "While this is indeed true in the case of..., the reality is that far more often..."). Otherwise you risking losing the thread of your argument and leaving your reader without a clear idea of what you're trying to say.