Like onehundred80 stated, you'll probably need a paint polish (Meguiar's Scratch-X kinda falls into this product line), finished up with a good wax and/or sealant. If the blemish is severe enough, you might have to start with a paint compound, then a polish to remove any swirls, followed by a good wax product. I use Meguiar's product line whenever I need to use this approach. If you have access to a buffer, makes the removal of a surface blemish somewhat easier. But it's not necessary in most cases.

Forgot to mention, in some cases, I will use a product like Prep-Sol to remove the wax in the spot before starting to deal with a blemish.