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1. The games usually last about 3 hours. It may be a tad under or a tad over. If the game is tied at the end of the ninth inning than the game will go into extra innings, which is the proverbial over time. Once it goes into extra innings, if the home team takes the lead, they automatically win. If the visiting team takes the lead, the home team will get half an inning to take the lead back and possibly overcome it and win. There's no saying when the game will end when the game is in extra innings.
2. If you're going to Fenway, the Star Spangled Banner, Sweet Caroline (by Neal Diamond) and Take Me Out To The Ballgame will be sung. The lyrics are usually on the big screen in center field and participating is completely optional.
3. There is food in and around Fenway that you'll likely not find anywhere else. It will be expensive in Fenway and likely expensive outside and near Fenway, but you have a lot of choices. The Fenway Frank is a favorite.