When people are planning a trip to Athens, the first worry that seems to come up is the fear of the protests. I'd be lying if I told you that these protest weren't a little dangerous, but really they're easy to avoid. Many tourist don't even notice them when visiting the popular sites. The protests often stay in pre planed areas (Syntagma Square, Omionia Square, and the areas around the Universities), and even when they get violent, it's often contained to very particular places.
Strikes in Athens can make life very difficult for tourists, particularly if they're un-aware. Many strikes only last for a day or less, but they can force you to change your plans at the last minute. Most notable strikes are:
Metro, bus and taxi strikes, for obvious reasons this can cut off any ground mobility you might have in the city, it also increases the traffic in the downtown area making it loud and crowded on the streets.
If they ferries are on strike and you have plans to visit one of the islands, your plans are sunk.
When tourist sites go on strike that means your visit to the Acropolis isn't happening, museums are also often closed as well.
Because strikes can pop up out of nowhere, the best plan in Athens is to get the sites you really can't miss over with as soon as possible, just in case you can't make it later. Ask at your hotel before you venture anywhere to make sure you wont run into any problems.