In short: Come to the airport early, security checks will take longer.
You should expect a longer and more serious security check before your departure and after your landing, including questioning about your whereabouts and activities in Iran or Kuwait. If you just visited there, this should be it - your entrance is very highly unlikely to be refused.
Predictive Profiling 101: Why are you being checked?
Unlike some other Middle Eastern countries, Israel does not ban or punish tourists who have visited certain countries in the past. This is a security measure, based on Predictive Profiling often used by Israeli air transportation security. This means that the passenger's personal details are aggregated, and if they fit into a presumably dangerous profile, the passenger is thoroughly questioned prior to boarding. This method is based on hundreds of variables (age, nationality, purpose of travel, ...), it's arbitrary and unpredictable by nature, so nobody knows know if Iranian stamp will raise more questions than a Kuwait stamp.
- Don't lie or hide details. Lying will probably get you into longer questioning, and you're more likely to get banned.
- Questions might get nosy and personal.
- The terminals for Israeli (and US) flights are often remote and isolated, especially in European airports. Taking a special in-airport bus to an unmarked terminal is not unusual. Do really come early.
- For further reading about the roots and disputes about Predictive Profiling, you can also read about Mike's Place and the Hindawi Affair, which are taught in security courses in Israel. This is not a political statement, just the viewpoint of the security official.
- On a last personal note, I envy you a little! Iran is supposed to be a truly beautiful country, a mixture of Asian and Middle Eastern geography. I hope I can visit it as a tourist, one day soon.