Many people visit the Holy Land every year, so it's certainly safe as long as you keep a few precautions in mind. A lot of it just comes down to prudence and common sense, really:
- You should definitely take a tour with an experienced guide.
- Read the travel advisory pages for Israel and its neighbors published by the U.S. State Department. You can find the advisory page for Israel here.
- Avoid crowded public transportation and public markets.
- Avoid demonstrations and sites with significant religious meaning to multiple faiths like the Temple Mount.
- Don't visit or photograph military areas. Also take care not to photograph the police, religious Muslims, and Orthodox Jews.
- Don't travel to the Gaza Strip. The West Bank should also be avoided.
- Take care to dress appropriately and mind religious customs, especially around ultra-Orthodox neighborhoods.