Undercover is not the best way to work. Revealing information if working undercover can be considered as a betrayal and put your life in danger. Be honest about what you do and you will do of the gathered information. Explain that you are a journalist and your duty is to report on “both sides of the story” to the media.
Protect your sources: when contacting them, do not use a personal or professional phone line computer, and even email. Avoid communication that can easily be traced. Try to get one of these anonymous disposable SIM cards for phone calls. You may only be after information but intelligence officers could be after you to find out about your sources.
Consider that when going to a meeting, you might be followed. Plan how you will get to the meeting place without traces. If you suspect something, do not attend the meeting.
Terrorist organizations have their own media people. Be aware that they will keep a record on your past and future activities and be transparent. A proven track of your publications will be the proof that you are a journalist and not a spy.
If you are asked to keep some information for yourself, try to get it from other sources, instead of convincing your original sources to reveal it.
Being of the same origin and cultural background of the terrorists is a way to fuse in their environment. Common cultural and religious values are good for confidences. Be respectful to culture and religion, dress alike, act alike and behave yourself, even when you are not working. You might be watched.
In Muslim world, being a woman can get some married men into trouble with their wives; but it also has advantages, men treat you with a lot of respect.
Family and relatives can provide interesting information to profile the personality of the organization or one of his members.
If the target is hard to approach, it is sometimes useful to cover completely different issues in the country of interest.