Hezbollah seems to have gotten a lot more than it bargained for, judging by how things are goin in Lebanon. The Israelis are pissed and rightfully are taking care of business. But what does this mean for Westerners not in the Middle East?
It's almost certain that there are Hezbollah sleeper cells in Western countries, the US included. If the current war widens, especially if Iran gets directly involved, it's very possible that those cells could go active. For example, the FBI sent out a warning earlier today that Hezbollah may target Jewish targets.
Preparing for a Hezbollah terrorist attack is problematical. If they launch an attack on US soil, for example, it's unlikely that they'd shoot off Katyusha rockets. Suicide bombings, shootings, or the use of WMD would be more likely. There's not much you can do to prepare for such an attack, unless it was a case of a terrorist going into a mall and shooting up the place. In such an attack a courageous person with a concealed pistol could have a chance of stopping it. (Although the idea of going up against an AK-47 armed terrorist with a pistol is not appealing.)
Preparing for the aftermath of terrorist attacks does make sense, however. Based on what happened in the immediate aftermath of 9/11 or the Washington, DC area sniper shootings, it's likely that a series of coordinated nationwide attacks would cause American commerce to grind to a halt. Depending upon the proximity to and the nature of a terrorist attack, some basic services may be interrupted. E.g., power outages or disruptions to the water supply. So, having stored food and water will be prudent.
In general, try to think like a terrorist. Ask yourself how you would cause the most fear and aggravation to your countrymen, and prepare accordingly.