The problem with windshield wipers is you don't think about them until you need them. And that usually isn't the best time to replace them.
Here's a quick guide on how to replace your blades -- and how blades differ.
The oldest type of windshield wiper frame often allows you to keep the frame and replace only the squeegee blade itself, which is the cheapest option. It does a good job in most conditions, but if you live in a snowy region, this claw structure can collect ice, which prevents it from forming to the windshield, leaving segments unwiped.
A simple alternative is a snow wiper designed especially for winter; it has this rubber sheath on it to prevent ice buildup.
Third is the beam style wiper blade, which is becoming very common on new cars. It's lower-profile than the others, it's better looking, it's less prone to letting ice build up.
A major difference with these alternative styles is that you replace the entire wiper -- arguably that’s a do-it-yourself project, but some styles are very difficult to deal with. The simplest types require just a pinch to release, or they may have a very visible button.
Trickier systems may hide their release tab. Don't sweat it; your mechanic can handle this for you, or national auto parts store chains are usually happy to send someone out to the parking lot to help install your newly purchased blades.
To be sure, change blades every spring and fall, and don't forget the rear one, either.